diff --git a/.github/workflows/haskell-ci.yml b/.github/workflows/haskell-ci.yml
index 105da1a7..e1d15085 100644
--- a/.github/workflows/haskell-ci.yml
+++ b/.github/workflows/haskell-ci.yml
@@ -8,9 +8,9 @@
 #
 # For more information, see https://github.com/haskell-CI/haskell-ci
 #
-# version: 0.19.20250506
+# version: 0.19.20260331
 #
-# REGENDATA ("0.19.20250506",["github","cabal.project"])
+# REGENDATA ("0.19.20260331",["github","cabal.project"])
 #
 name: Haskell-CI
 on:
@@ -20,6 +20,11 @@ on:
   pull_request:
     branches:
       - master
+  merge_group:
+    branches:
+      - master
+  workflow_dispatch:
+    {}
 jobs:
   linux:
     name: Haskell-CI - Linux - ${{ matrix.compiler }}
@@ -27,41 +32,46 @@ jobs:
     timeout-minutes:
       60
     container:
-      image: buildpack-deps:focal
+      image: buildpack-deps:jammy
     continue-on-error: ${{ matrix.allow-failure }}
     strategy:
       matrix:
         include:
-          - compiler: ghc-9.12.1
+          - compiler: ghc-9.14.1
             compilerKind: ghc
-            compilerVersion: 9.12.1
+            compilerVersion: 9.14.1
             setup-method: ghcup
             allow-failure: true
-          - compiler: ghc-9.10.2
+          - compiler: ghc-9.12.4
             compilerKind: ghc
-            compilerVersion: 9.10.2
+            compilerVersion: 9.12.4
             setup-method: ghcup
-            allow-failure: true
-          - compiler: ghc-9.8.1
+            allow-failure: false
+          - compiler: ghc-9.10.3
             compilerKind: ghc
-            compilerVersion: 9.8.1
+            compilerVersion: 9.10.3
             setup-method: ghcup
-            allow-failure: true
-          - compiler: ghc-9.6.3
+            allow-failure: false
+          - compiler: ghc-9.8.4
             compilerKind: ghc
-            compilerVersion: 9.6.3
+            compilerVersion: 9.8.4
             setup-method: ghcup
-            allow-failure: true
+            allow-failure: false
+          - compiler: ghc-9.6.7
+            compilerKind: ghc
+            compilerVersion: 9.6.7
+            setup-method: ghcup
+            allow-failure: false
           - compiler: ghc-9.4.8
             compilerKind: ghc
             compilerVersion: 9.4.8
             setup-method: ghcup
-            allow-failure: true
+            allow-failure: false
           - compiler: ghc-9.2.8
             compilerKind: ghc
             compilerVersion: 9.2.8
             setup-method: ghcup
-            allow-failure: true
+            allow-failure: false
           - compiler: ghc-9.0.2
             compilerKind: ghc
             compilerVersion: 9.0.2
@@ -82,17 +92,12 @@ jobs:
             compilerVersion: 8.6.5
             setup-method: ghcup
             allow-failure: false
-          - compiler: ghc-8.4.4
-            compilerKind: ghc
-            compilerVersion: 8.4.4
-            setup-method: ghcup
-            allow-failure: false
       fail-fast: false
     steps:
       - name: apt-get install
         run: |
           apt-get update
-          apt-get install -y --no-install-recommends gnupg ca-certificates dirmngr curl git software-properties-common libtinfo5 libnuma-dev
+          apt-get install -y --no-install-recommends gnupg ca-certificates dirmngr curl git software-properties-common libtinfo5
       - name: Install GHCup
         run: |
           mkdir -p "$HOME/.ghcup/bin"
@@ -100,8 +105,8 @@ jobs:
           chmod a+x "$HOME/.ghcup/bin/ghcup"
       - name: Install cabal-install
         run: |
-          "$HOME/.ghcup/bin/ghcup" install cabal 3.14.2.0 || (cat "$HOME"/.ghcup/logs/*.* && false)
-          echo "CABAL=$HOME/.ghcup/bin/cabal-3.14.2.0 -vnormal+nowrap" >> "$GITHUB_ENV"
+          "$HOME/.ghcup/bin/ghcup" install cabal 3.16.0.0 || (cat "$HOME"/.ghcup/logs/*.* && false)
+          echo "CABAL=$HOME/.ghcup/bin/cabal-3.16.0.0 -vnormal+nowrap" >> "$GITHUB_ENV"
       - name: Install GHC (GHCup)
         if: matrix.setup-method == 'ghcup'
         run: |
@@ -177,7 +182,7 @@ jobs:
           chmod a+x $HOME/.cabal/bin/cabal-plan
           cabal-plan --version
       - name: checkout
-        uses: actions/checkout@v4
+        uses: actions/checkout@v5
         with:
           path: source
       - name: initial cabal.project for sdist
@@ -202,7 +207,9 @@ jobs:
           touch cabal.project.local
           echo "packages: ${PKGDIR_openapi3}" >> cabal.project
           echo "package openapi3" >> cabal.project
-          echo "    ghc-options: -Werror=missing-methods" >> cabal.project
+          echo "    ghc-options: -Werror=missing-methods -Werror=missing-fields" >> cabal.project
+          if [ $((HCNUMVER >= 90000)) -ne 0 ] ; then echo "package openapi3" >> cabal.project ; fi
+          if [ $((HCNUMVER >= 90000)) -ne 0 ] ; then echo "    ghc-options: -Werror=incomplete-patterns -Werror=incomplete-uni-patterns" >> cabal.project ; fi
           cat >> cabal.project <<EOF
           EOF
           $HCPKG list --simple-output --names-only | perl -ne 'for (split /\s+/) { print "constraints: any.$_ installed\n" unless /^(openapi3)$/; }' >> cabal.project.local
@@ -245,6 +252,18 @@ jobs:
       - name: prepare for constraint sets
         run: |
           rm -f cabal.project.local
+      - name: constraint set insert-ordered-containers-0.3
+        run: |
+          $CABAL v2-build $ARG_COMPILER --disable-tests --disable-benchmarks --constraint='insert-ordered-containers >=0.3' all --dry-run
+          cabal-plan topo | sort
+          $CABAL v2-build $ARG_COMPILER --disable-tests --disable-benchmarks --constraint='insert-ordered-containers >=0.3' --dependencies-only -j2 all
+          $CABAL v2-build $ARG_COMPILER --disable-tests --disable-benchmarks --constraint='insert-ordered-containers >=0.3' all
+      - name: constraint set insert-ordered-containers-0.2
+        run: |
+          $CABAL v2-build $ARG_COMPILER --disable-tests --disable-benchmarks --constraint='insert-ordered-containers <0.3' all --dry-run
+          cabal-plan topo | sort
+          $CABAL v2-build $ARG_COMPILER --disable-tests --disable-benchmarks --constraint='insert-ordered-containers <0.3' --dependencies-only -j2 all
+          $CABAL v2-build $ARG_COMPILER --disable-tests --disable-benchmarks --constraint='insert-ordered-containers <0.3' all
       - name: constraint set aeson-2
         run: |
           $CABAL v2-build $ARG_COMPILER --disable-tests --disable-benchmarks --constraint='aeson >=2.0' all --dry-run
diff --git a/cabal.haskell-ci b/cabal.haskell-ci
index ea783c4c..f2053cc8 100644
--- a/cabal.haskell-ci
+++ b/cabal.haskell-ci
@@ -1,7 +1,6 @@
 branches: master
 
-distribution: focal
-allow-failures: >=9.2
+allow-failures: >=9.14
 
 -- https://github.com/haskell-CI/haskell-ci/issues/658#issuecomment-1513692337
 haddock-components: libs
@@ -11,9 +10,18 @@ haddock-components: libs
 -- and https://github.com/haskell/cabal/issues/8707
 haddock: < 9.0 || >= 9.4
 
+-- Breaks on doctests
+error-unused-packages: False
+
 constraint-set aeson-1
   constraints: aeson <2.0
   ghc: <9.2
 
 constraint-set aeson-2
   constraints: aeson >=2.0
+
+constraint-set insert-ordered-containers-0.2
+  constraints: insert-ordered-containers <0.3
+
+constraint-set insert-ordered-containers-0.3
+  constraints: insert-ordered-containers >=0.3
diff --git a/openapi3.cabal b/openapi3.cabal
index 1185d038..726feaba 100644
--- a/openapi3.cabal
+++ b/openapi3.cabal
@@ -23,17 +23,17 @@ extra-source-files:
   , CHANGELOG.md
   , examples/*.hs
 tested-with:
-  GHC ==8.4.4
-   || ==8.6.5
+  GHC ==8.6.5
    || ==8.8.4
    || ==8.10.7
    || ==9.0.2
    || ==9.2.8
    || ==9.4.8
-   || ==9.6.3
-   || ==9.8.1
-   || ==9.10.2
-   || ==9.12.1
+   || ==9.6.7
+   || ==9.8.4
+   || ==9.10.3
+   || ==9.12.4
+   || ==9.14.1
 
 custom-setup
   setup-depends:
@@ -65,14 +65,15 @@ library
     Data.OpenApi.Internal.TypeShape
 
     Data.OpenApi.Aeson.Compat
+    Data.HashMap.Strict.InsOrd.Compat
 
   -- GHC boot libraries
   build-depends:
-      base             >=4.11.1.0  && <4.22
+      base             >=4.11.1.0  && <4.23
     , bytestring       >=0.10.8.2  && <0.13
     , containers       >=0.5.11.0  && <0.9
-    , template-haskell >=2.13.0.0  && <2.24
-    , time             >=1.8.0.2   && <1.15
+    , template-haskell >=2.13.0.0  && <2.25
+    , time             >=1.8.0.2   && <1.16
     , transformers     >=0.5.5.0   && <0.7
 
   build-depends:
@@ -81,7 +82,7 @@ library
 
   -- other dependencies
   build-depends:
-      base-compat-batteries     >=0.11.1   && <0.15
+      base-compat-batteries     >=0.11.1   && <0.16
     , aeson                     >=1.4.2.0  && <1.6 || >=2.0.1.0 && < 2.3
     , aeson-pretty              >=0.8.7    && <0.9
     -- cookie 0.4.3 is needed by GHC 7.8 due to time>=1.4 constraint
@@ -89,7 +90,7 @@ library
     , generics-sop              >=0.5.1.0  && <0.6
     , hashable                  >=1.2.7.0  && <1.6
     , http-media                >=0.8.0.0  && <0.9
-    , insert-ordered-containers >=0.2.3    && <0.3
+    , insert-ordered-containers >=0.2.3    && <0.4
     , lens                      >=4.16.1   && <5.4
     , optics-core               >=0.2      && <0.5
     , optics-th                 >=0.2      && <0.5
@@ -97,9 +98,43 @@ library
     , unordered-containers      >=0.2.9.0  && <0.3
     , uuid-types                >=1.0.3    && <1.1
     , vector                    >=0.12.0.1 && <0.14
-    , QuickCheck                >=2.10.1   && <2.16
+    , QuickCheck                >=2.10.1   && <2.19
 
   default-language:    Haskell2010
+  default-extensions:
+    ConstraintKinds
+    DataKinds
+    DefaultSignatures
+    DeriveDataTypeable
+    DeriveFunctor
+    DeriveGeneric
+    DeriveTraversable
+    ExplicitForAll
+    FlexibleContexts
+    FlexibleInstances
+    FunctionalDependencies
+    GADTs
+    GeneralizedNewtypeDeriving
+    KindSignatures
+    LambdaCase
+    MultiParamTypeClasses
+    OverloadedLabels
+    OverloadedStrings
+    PackageImports
+    PolyKinds
+    RankNTypes
+    RecordWildCards
+    ScopedTypeVariables
+    StandaloneDeriving
+    TemplateHaskell
+    TupleSections
+    TypeApplications
+    TypeFamilies
+    TypeOperators
+    TypeSynonymInstances
+    UndecidableInstances
+    UndecidableSuperClasses
+    ViewPatterns
 
 test-suite spec
   type:             exitcode-stdio-1.0
@@ -155,6 +190,7 @@ test-suite doctests
   main-is:          doctests.hs
   type:             exitcode-stdio-1.0
   build-depends:    base, openapi3
+  ghc-options:      -Wno-unused-packages
 
 executable example
   hs-source-dirs:   examples
diff --git a/src/Data/HashMap/Strict/InsOrd/Compat.hs b/src/Data/HashMap/Strict/InsOrd/Compat.hs
new file mode 100644
index 00000000..e6fabead
--- /dev/null
+++ b/src/Data/HashMap/Strict/InsOrd/Compat.hs
@@ -0,0 +1,438 @@
+-- Ported from GetShopTV/swagger2 (pull request #262) to apply the same
+-- insert-ordered-containers-0.3 compatibility fix to openapi3.
+-- Credit for the design and implementation belongs to the swagger2 authors.
+{-# LANGUAGE CPP #-}
+-- |
+-- Module:      Data.HashMap.Strict.InsOrd.Compat
+-- Maintainer:  Nickolay Kudasov <nickolay@getshoptv.com>
+-- Stability:   experimental
+--
+-- Compatibility wrapper around @insert-ordered-containers@ to mitigate the
+-- breaking changes introduced in @insert-ordered-containers-0.3.0@:
+-- <https://github.com/erikd/insert-ordered-containers/pull/8>.
+--
+-- That change fixed 'Eq' and Aeson instances in the upstream package, but it is
+-- a behavioral break for @swagger2@ where we need stable Swagger Schema
+-- generation and JSON object-like encoding.
+--
+-- This module keeps the old @swagger2@ expectations:
+--
+-- * 'InsOrdHashMap' values are encoded as JSON objects (not arrays of key/value
+--   tuples), so field names remain first-class object keys.
+-- * Equality intentionally ignores insertion order (compares as plain hash
+--   maps), which matches how many tests currently assert JSON equality.
+--
+-- Simple encoding examples:
+--
+-- >>> import Data.Aeson (encode, eitherDecode)
+-- >>> import qualified Data.ByteString.Lazy.Char8 as BSL8
+-- >>> import qualified Data.HashMap.Strict as HM
+-- >>> import qualified Data.HashMap.Strict.InsOrd.Compat as IOHM
+-- >>> let decodeIOHM s = either error id (eitherDecode (BSL8.pack s) :: Either String (IOHM.InsOrdHashMap String Int))
+--
+-- A regular hash map has no insertion order guarantee:
+--
+-- >>> encode (HM.fromList [("a", 1 :: Int), ("b", 2)])
+-- "{\"a\":1,\"b\":2}"
+-- >>> encode (HM.fromList [("b", 1 :: Int), ("a", 2)])
+-- "{\"a\":2,\"b\":1}"
+--
+-- Our compat 'InsOrdHashMap' encodes to a JSON object as well, but preserves insertion order:
+--
+-- >>> encode (IOHM.fromList [("a", 1 :: Int), ("b", 2)])
+-- "{\"a\":1,\"b\":2}"
+-- >>> encode (IOHM.fromList [("b", 1 :: Int), ("a", 2)])
+-- "{\"b\":1,\"a\":2}"
+--
+-- Round-tripping through decode/encode demonstrates the caveat: encoding
+-- preserves insertion order, but decoded object key order is not guaranteed.
+--
+-- >>> encode (decodeIOHM "{\"a\":1,\"b\":2}")
+-- "{\"a\":1,\"b\":2}"
+-- >>> encode (decodeIOHM "{\"b\":1,\"a\":2}")
+-- "{\"a\":2,\"b\":1}"
+--
+-- This object encoding is what @swagger2@ wants for generated Swagger
+-- definitions/properties because it keeps emitted schemas easy to consume and
+-- stable in practice.
+--
+-- Important caveat: decoding cannot be fully stable with respect to insertion
+-- order due to @aeson@ limitations. In particular, object parsing goes through
+-- structures that do not preserve all ordering guarantees end-to-end. We accept
+-- this trade-off for now because the primary requirement is deterministic
+-- /encoding/ for generated Swagger Schema artifacts.
+--
+-- Many tests rely on @aesonQQ@-style JSON equality, where semantic object
+-- equality matters more than insertion order. Comparing via plain hash maps
+-- makes those tests robust under benign key-order variation. This is a weaker
+-- notion of equality and hopefully will be revisited later.
+module Data.HashMap.Strict.InsOrd.Compat (
+  InsOrdHashMap,
+  -- * Construction
+  empty,
+  singleton,
+  -- * Basic interface
+  null,
+  size,
+  member,
+  lookup,
+  lookupDefault,
+  insert,
+  insertWith,
+  delete,
+  adjust,
+  update,
+  alter,
+  -- * Combine
+  union,
+  unionWith,
+  unionWithKey,
+  unions,
+  -- * Transformations
+  map,
+  mapKeys,
+  traverseKeys,
+  mapWithKey,
+  traverseWithKey,
+  -- ** Unordered
+  unorderedTraverse,
+  unorderedTraverseWithKey,
+  -- * Difference and intersection
+  difference,
+  intersection,
+  intersectionWith,
+  intersectionWithKey,
+  -- * Folds
+  foldl',
+  foldlWithKey',
+  foldr,
+  foldrWithKey,
+  foldMapWithKey,
+  -- ** Unordered
+  unorderedFoldMap,
+  unorderedFoldMapWithKey,
+  -- * Filter
+  filter,
+  filterWithKey,
+  mapMaybe,
+  mapMaybeWithKey,
+  -- * Conversions
+  keys,
+  elems,
+  toList,
+  toRevList,
+  fromList,
+  toHashMap,
+  fromHashMap,
+  -- * Lenses
+  hashMap,
+  unorderedTraversal,
+  -- * Debugging
+  valid,
+  ) where
+
+#if !MIN_VERSION_insert_ordered_containers(0,3,0)
+import Prelude hiding (null, lookup, map, foldl', foldr, filter)
+import Data.HashMap.Strict.InsOrd
+#else
+import qualified Data.HashMap.Strict.InsOrd as InsOrdHashMap
+
+import Prelude hiding (null, size, member, lookup, lookupDefault, map, foldl', filter)
+import qualified Prelude
+
+import qualified Data.Aeson as A
+import qualified Data.Aeson.Encoding as E
+import           Data.HashMap.Strict (HashMap)
+import qualified Data.HashMap.Strict as HashMap
+
+import qualified GHC.Exts as Exts
+
+import Data.Data                       (Data)
+import Data.Foldable                   (Foldable (foldMap))
+import Data.Hashable                   (Hashable (..))
+
+import qualified Control.Lens        as Lens
+import Control.Lens
+       (At (..), Index, Iso, IxValue, Ixed (..), Traversal, _1, _2, iso, (<&>))
+
+import qualified Optics.Core         as Optics
+
+newtype InsOrdHashMap k v = InsOrdHashMap { unCompatInsOrdHashMap :: InsOrdHashMap.InsOrdHashMap k v }
+  deriving (Show, Read, Data, Functor, Foldable, Traversable, Semigroup, Monoid)
+
+instance (Eq k, Eq v) => Eq (InsOrdHashMap k v) where
+    a == b = toHashMap a == toHashMap b
+
+instance (Eq k, Hashable k) => Exts.IsList (InsOrdHashMap k v) where
+    type Item (InsOrdHashMap k v) = Exts.Item (InsOrdHashMap.InsOrdHashMap k v)
+    fromList = InsOrdHashMap . InsOrdHashMap.fromList
+    toList   = InsOrdHashMap.toList . unCompatInsOrdHashMap
+
+-------------------------------------------------------------------------------
+-- Aeson
+-------------------------------------------------------------------------------
+
+instance (A.ToJSONKey k) => A.ToJSON1 (InsOrdHashMap k) where
+    liftToJSON _ t _ = case A.toJSONKey :: A.ToJSONKeyFunction k of
+      A.ToJSONKeyText f _ -> A.object . fmap (\(k, v) -> (f k, t v)) . toList
+      A.ToJSONKeyValue f _ -> A.toJSON . fmap (\(k,v) -> A.toJSON (f k, t v)) . toList
+
+    liftToEncoding o t _ = case A.toJSONKey :: A.ToJSONKeyFunction k of
+      A.ToJSONKeyText _ f ->  E.dict f t foldrWithKey
+      A.ToJSONKeyValue _ f -> E.list (A.liftToEncoding2 (const False) f (E.list f) o t (E.list t)) . toList
+
+instance (A.ToJSONKey k, A.ToJSON v) => A.ToJSON (InsOrdHashMap k v) where
+    toJSON = A.toJSON1
+    toEncoding = A.toEncoding1
+
+-------------------------------------------------------------------------------
+
+instance (Eq k, Hashable k, A.FromJSONKey k) => A.FromJSON1 (InsOrdHashMap k) where
+    liftParseJSON o p pl v = fromList . HashMap.toList <$> A.liftParseJSON o p pl v
+
+instance (Eq k, Hashable k, A.FromJSONKey k, A.FromJSON v) => A.FromJSON (InsOrdHashMap k v) where
+    parseJSON = A.parseJSON1
+
+-------------------------------------------------------------------------------
+-- indexed-traversals
+-------------------------------------------------------------------------------
+
+instance (Eq k, Hashable k) => Optics.FunctorWithIndex k (InsOrdHashMap k) where
+    imap = mapWithKey
+instance (Eq k, Hashable k) => Optics.FoldableWithIndex k (InsOrdHashMap k) where
+    ifoldMap = foldMapWithKey
+    ifoldr   = foldrWithKey
+instance (Eq k, Hashable k) => Optics.TraversableWithIndex k (InsOrdHashMap k) where
+    itraverse = traverseWithKey
+
+-------------------------------------------------------------------------------
+-- Lens
+-------------------------------------------------------------------------------
+
+type instance Index (InsOrdHashMap k v) = k
+type instance IxValue (InsOrdHashMap k v) = v
+
+instance (Eq k, Hashable k) => Ixed (InsOrdHashMap k v) where
+    ix k f m = ixImpl k pure f m
+    {-# INLINABLE ix #-}
+
+ixImpl
+  :: (Eq k, Hashable k, Functor f)
+  => k
+  -> (InsOrdHashMap k v -> f (InsOrdHashMap k v))
+  -> (v -> f v)
+  -> InsOrdHashMap k v
+  -> f (InsOrdHashMap k v)
+ixImpl k point f m = case lookup k m of
+    Just v  -> f v <&> \v' -> insert k v' m
+    Nothing -> point m
+{-# INLINE ixImpl #-}
+
+instance (Eq k, Hashable k) => At (InsOrdHashMap k a) where
+    at k f m = f mv <&> \r -> case r of
+        Nothing -> maybe m (const (delete k m)) mv
+        Just v' -> insert k v' m
+      where mv = lookup k m
+    {-# INLINABLE at #-}
+
+-------------------------------------------------------------------------------
+-- Optics
+-------------------------------------------------------------------------------
+
+type instance Optics.Index (InsOrdHashMap k v) = k
+type instance Optics.IxValue (InsOrdHashMap k v) = v
+
+instance (Eq k, Hashable k) => Optics.Ixed (InsOrdHashMap k v) where
+    ix k = Optics.atraversalVL $ \point f m -> ixImpl k point f m
+    {-# INLINE ix #-}
+
+instance (Eq k, Hashable k) => Optics.At (InsOrdHashMap k a) where
+    at k = Optics.lensVL $ \f m -> Lens.at k f m
+    {-# INLINE at #-}
+
+-------------------------------------------------------------------------------
+
+-- | This is a slight lie, as roundtrip doesn't preserve ordering.
+hashMap :: Iso (InsOrdHashMap k a) (InsOrdHashMap k b) (HashMap k a) (HashMap k b)
+hashMap = iso toHashMap fromHashMap
+
+unorderedTraversal :: Traversal (InsOrdHashMap k a) (InsOrdHashMap k b) a b
+unorderedTraversal = hashMap . traverse
+
+-------------------------------------------------------------------------------
+-- * Construction
+-------------------------------------------------------------------------------
+
+empty :: InsOrdHashMap k v
+empty = InsOrdHashMap InsOrdHashMap.empty
+
+singleton :: Hashable k => k -> v -> InsOrdHashMap k v
+singleton k v = InsOrdHashMap (InsOrdHashMap.singleton k v)
+
+-------------------------------------------------------------------------------
+-- * Basic interface
+-------------------------------------------------------------------------------
+
+null :: InsOrdHashMap k v -> Bool
+null = InsOrdHashMap.null . unCompatInsOrdHashMap
+
+size :: InsOrdHashMap k v -> Int
+size = InsOrdHashMap.size . unCompatInsOrdHashMap
+
+insert :: Hashable k => k -> v -> InsOrdHashMap k v -> InsOrdHashMap k v
+insert k v = InsOrdHashMap . InsOrdHashMap.insert k v . unCompatInsOrdHashMap
+
+insertWith :: Hashable k => (v -> v -> v) -> k -> v -> InsOrdHashMap k v -> InsOrdHashMap k v
+insertWith f k v = InsOrdHashMap . InsOrdHashMap.insertWith f k v . unCompatInsOrdHashMap
+
+delete :: Hashable k => k -> InsOrdHashMap k v -> InsOrdHashMap k v
+delete k = InsOrdHashMap . InsOrdHashMap.delete k . unCompatInsOrdHashMap
+
+adjust :: Hashable k => (v -> v) -> k -> InsOrdHashMap k v -> InsOrdHashMap k v
+adjust f k = InsOrdHashMap . InsOrdHashMap.adjust f k . unCompatInsOrdHashMap
+
+update :: Hashable k => (v -> Maybe v) -> k -> InsOrdHashMap k v -> InsOrdHashMap k v
+update f k = InsOrdHashMap . InsOrdHashMap.update f k . unCompatInsOrdHashMap
+
+alter :: Hashable k => (Maybe v -> Maybe v) -> k -> InsOrdHashMap k v -> InsOrdHashMap k v
+alter f k = InsOrdHashMap . InsOrdHashMap.alter f k . unCompatInsOrdHashMap
+
+member :: Hashable k => k -> InsOrdHashMap k v -> Bool
+member k = InsOrdHashMap.member k . unCompatInsOrdHashMap
+
+lookup :: Hashable k => k -> InsOrdHashMap k v -> Maybe v
+lookup k = InsOrdHashMap.lookup k . unCompatInsOrdHashMap
+
+lookupDefault :: Hashable k => v -> k -> InsOrdHashMap k v -> v
+lookupDefault k def = InsOrdHashMap.lookupDefault k def . unCompatInsOrdHashMap
+
+-- * Combine
+
+union :: Hashable k => InsOrdHashMap k v -> InsOrdHashMap k v -> InsOrdHashMap k v
+union m1 m2 = InsOrdHashMap (InsOrdHashMap.union (unCompatInsOrdHashMap m1) (unCompatInsOrdHashMap m2))
+
+unionWith :: Hashable k => (v -> v -> v) -> InsOrdHashMap k v -> InsOrdHashMap k v -> InsOrdHashMap k v
+unionWith f m1 m2 = InsOrdHashMap (InsOrdHashMap.unionWith f (unCompatInsOrdHashMap m1) (unCompatInsOrdHashMap m2))
+
+unionWithKey :: Hashable k => (k -> v -> v -> v) -> InsOrdHashMap k v -> InsOrdHashMap k v -> InsOrdHashMap k v
+unionWithKey f m1 m2 = InsOrdHashMap (InsOrdHashMap.unionWithKey f (unCompatInsOrdHashMap m1) (unCompatInsOrdHashMap m2))
+
+unions :: Hashable k => [InsOrdHashMap k v] -> InsOrdHashMap k v
+unions = InsOrdHashMap . InsOrdHashMap.unions . Prelude.map unCompatInsOrdHashMap
+
+-------------------------------------------------------------------------------
+-- * Transformations
+-------------------------------------------------------------------------------
+
+map :: (v -> v) -> InsOrdHashMap k v -> InsOrdHashMap k v
+map f = InsOrdHashMap . InsOrdHashMap.map f . unCompatInsOrdHashMap
+
+mapKeys :: Hashable k => (k -> k) -> InsOrdHashMap k v -> InsOrdHashMap k v
+mapKeys f = InsOrdHashMap . InsOrdHashMap.mapKeys f . unCompatInsOrdHashMap
+
+traverseKeys :: (Applicative f, Hashable k) => (k -> f k) -> InsOrdHashMap k v -> f (InsOrdHashMap k v)
+traverseKeys f = fmap InsOrdHashMap . InsOrdHashMap.traverseKeys f . unCompatInsOrdHashMap
+
+mapWithKey :: (k -> v1 -> v2) -> InsOrdHashMap k v1 -> InsOrdHashMap k v2
+mapWithKey f = InsOrdHashMap . InsOrdHashMap.mapWithKey f . unCompatInsOrdHashMap
+
+traverseWithKey :: (Applicative f, Hashable k) => (k -> v1 -> f v2) -> InsOrdHashMap k v1 -> f (InsOrdHashMap k v2)
+traverseWithKey f = fmap InsOrdHashMap . InsOrdHashMap.traverseWithKey f . unCompatInsOrdHashMap
+
+-- ** Unordered
+
+unorderedTraverse :: (Applicative f, Hashable k) => (v -> f v) -> InsOrdHashMap k v -> f (InsOrdHashMap k v)
+unorderedTraverse f = fmap InsOrdHashMap . InsOrdHashMap.unorderedTraverse f . unCompatInsOrdHashMap
+
+unorderedTraverseWithKey :: (Applicative f, Hashable k) => (k -> v -> f v) -> InsOrdHashMap k v -> f (InsOrdHashMap k v)
+unorderedTraverseWithKey f = fmap InsOrdHashMap . InsOrdHashMap.unorderedTraverseWithKey f . unCompatInsOrdHashMap
+
+-------------------------------------------------------------------------------
+-- * Difference and intersection
+-------------------------------------------------------------------------------
+
+difference :: Hashable k => InsOrdHashMap k v -> InsOrdHashMap k v -> InsOrdHashMap k v
+difference m1 m2 = InsOrdHashMap (InsOrdHashMap.difference (unCompatInsOrdHashMap m1) (unCompatInsOrdHashMap m2))
+
+intersection :: Hashable k => InsOrdHashMap k v -> InsOrdHashMap k v -> InsOrdHashMap k v
+intersection m1 m2 = InsOrdHashMap (InsOrdHashMap.intersection (unCompatInsOrdHashMap m1) (unCompatInsOrdHashMap m2))
+
+intersectionWith :: Hashable k => (v -> v -> v) -> InsOrdHashMap k v -> InsOrdHashMap k v -> InsOrdHashMap k v
+intersectionWith f m1 m2 = InsOrdHashMap (InsOrdHashMap.intersectionWith f (unCompatInsOrdHashMap m1) (unCompatInsOrdHashMap m2))
+
+intersectionWithKey :: Hashable k => (k -> v -> v -> v) -> InsOrdHashMap k v -> InsOrdHashMap k v -> InsOrdHashMap k v
+intersectionWithKey f m1 m2 = InsOrdHashMap (InsOrdHashMap.intersectionWithKey f (unCompatInsOrdHashMap m1) (unCompatInsOrdHashMap m2))
+
+-------------------------------------------------------------------------------
+-- * Folds
+-------------------------------------------------------------------------------
+
+foldl' :: (a -> v -> a) -> a -> InsOrdHashMap k v -> a
+foldl' f z = InsOrdHashMap.foldl' f z . unCompatInsOrdHashMap
+
+foldlWithKey' :: (a -> k -> v -> a) -> a -> InsOrdHashMap k v -> a
+foldlWithKey' f z = InsOrdHashMap.foldlWithKey' f z . unCompatInsOrdHashMap
+
+foldMapWithKey :: Monoid m => (k -> v -> m) -> InsOrdHashMap k v -> m
+foldMapWithKey f = InsOrdHashMap.foldMapWithKey f . unCompatInsOrdHashMap
+
+foldrWithKey :: (k -> v -> a -> a) -> a -> InsOrdHashMap k v -> a
+foldrWithKey f z = InsOrdHashMap.foldrWithKey f z . unCompatInsOrdHashMap
+
+-- ** Unordered
+
+unorderedFoldMap :: Monoid m => (v -> m) -> InsOrdHashMap k v -> m
+unorderedFoldMap f = InsOrdHashMap.unorderedFoldMap f . unCompatInsOrdHashMap
+
+unorderedFoldMapWithKey :: Monoid m => (k -> v -> m) -> InsOrdHashMap k v -> m
+unorderedFoldMapWithKey f = InsOrdHashMap.unorderedFoldMapWithKey f . unCompatInsOrdHashMap
+
+-------------------------------------------------------------------------------
+-- * Filter
+-------------------------------------------------------------------------------
+
+filter :: (v -> Bool) -> InsOrdHashMap k v -> InsOrdHashMap k v
+filter f = InsOrdHashMap . InsOrdHashMap.filter f . unCompatInsOrdHashMap
+
+filterWithKey :: (k -> v -> Bool) -> InsOrdHashMap k v -> InsOrdHashMap k v
+filterWithKey f = InsOrdHashMap . InsOrdHashMap.filterWithKey f . unCompatInsOrdHashMap
+
+mapMaybe :: (v -> Maybe v) -> InsOrdHashMap k v -> InsOrdHashMap k v
+mapMaybe f = InsOrdHashMap . InsOrdHashMap.mapMaybe f . unCompatInsOrdHashMap
+
+mapMaybeWithKey :: (k -> v -> Maybe v) -> InsOrdHashMap k v -> InsOrdHashMap k v
+mapMaybeWithKey f = InsOrdHashMap . InsOrdHashMap.mapMaybeWithKey f . unCompatInsOrdHashMap
+
+-------------------------------------------------------------------------------
+-- * Conversions
+-------------------------------------------------------------------------------
+
+keys :: InsOrdHashMap k v -> [k]
+keys = InsOrdHashMap.keys . unCompatInsOrdHashMap
+
+elems :: InsOrdHashMap k v -> [v]
+elems = InsOrdHashMap.elems . unCompatInsOrdHashMap
+
+toRevList :: InsOrdHashMap k v -> [(k, v)]
+toRevList = InsOrdHashMap.toRevList . unCompatInsOrdHashMap
+
+fromList :: Hashable k => [(k, v)] -> InsOrdHashMap k v
+fromList = InsOrdHashMap . InsOrdHashMap.fromList
+
+toList :: InsOrdHashMap k v -> [(k, v)]
+toList = InsOrdHashMap.toList . unCompatInsOrdHashMap
+
+toHashMap :: InsOrdHashMap k v -> HashMap k v
+toHashMap = InsOrdHashMap.toHashMap . unCompatInsOrdHashMap
+
+fromHashMap :: HashMap k v -> InsOrdHashMap k v
+fromHashMap = InsOrdHashMap . InsOrdHashMap.fromHashMap
+
+-------------------------------------------------------------------------------
+-- * Debugging
+-------------------------------------------------------------------------------
+
+valid :: (Eq k, Hashable k) => InsOrdHashMap k v -> Bool
+valid = InsOrdHashMap.valid . unCompatInsOrdHashMap
+
+#endif
diff --git a/src/Data/OpenApi.hs b/src/Data/OpenApi.hs
index a9ce8f3d..c4d825cc 100644
--- a/src/Data/OpenApi.hs
+++ b/src/Data/OpenApi.hs
@@ -139,7 +139,7 @@ import Data.OpenApi.Internal
 -- >>> import qualified Data.ByteString.Lazy.Char8 as BSL
 -- >>> import Data.OpenApi.Internal
 -- >>> import Data.OpenApi.Internal.Schema
--- >>> import qualified Data.HashMap.Strict.InsOrd as IOHM
+-- >>> import qualified Data.HashMap.Strict.InsOrd.Compat as IOHM
 -- >>> import Data.OpenApi.Internal.Utils
 -- >>> import Data.OpenApi.Lens
 -- >>> :set -XDeriveGeneric
diff --git a/src/Data/OpenApi/Aeson/Compat.hs b/src/Data/OpenApi/Aeson/Compat.hs
index c516a4e1..21387d27 100644
--- a/src/Data/OpenApi/Aeson/Compat.hs
+++ b/src/Data/OpenApi/Aeson/Compat.hs
@@ -10,7 +10,7 @@ import qualified Data.Aeson.KeyMap as KeyMap
 import qualified Data.HashMap.Strict as HM
 #endif
 import           Data.Bifunctor             (first)
-import qualified Data.HashMap.Strict.InsOrd as InsOrdHashMap
+import qualified Data.HashMap.Strict.InsOrd.Compat as InsOrdHashMap
 import qualified Data.Text                  as T
 
 #if MIN_VERSION_aeson(2,0,0)
diff --git a/src/Data/OpenApi/Declare.hs b/src/Data/OpenApi/Declare.hs
index a302bb0a..df9ef8d3 100644
--- a/src/Data/OpenApi/Declare.hs
+++ b/src/Data/OpenApi/Declare.hs
@@ -1,8 +1,3 @@
-{-# LANGUAGE DeriveFunctor #-}
-{-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE FunctionalDependencies #-}
-{-# LANGUAGE MultiParamTypeClasses #-}
-{-# LANGUAGE UndecidableInstances #-}
 -- |
 -- Module:      Data.OpenApi.Declare
 -- Maintainer:  Nickolay Kudasov <nickolay@getshoptv.com>
@@ -52,7 +47,6 @@ instance (Applicative m, Monad m, Monoid d) => Applicative (DeclareT d m) where
     return (mappend d' d'', f x)
 
 instance (Applicative m, Monad m, Monoid d) => Monad (DeclareT d m) where
-  return x = DeclareT (\_ -> pure (mempty, x))
   DeclareT dx >>= f = DeclareT $ \d -> do
     ~(d',  x) <- dx d
     ~(d'', y) <- runDeclareT (f x) (mappend d d')
diff --git a/src/Data/OpenApi/Internal.hs b/src/Data/OpenApi/Internal.hs
index b9be5292..be77723b 100644
--- a/src/Data/OpenApi/Internal.hs
+++ b/src/Data/OpenApi/Internal.hs
@@ -1,19 +1,5 @@
 {-# LANGUAGE CPP #-}
-{-# LANGUAGE DataKinds #-}
-{-# LANGUAGE DeriveDataTypeable #-}
-{-# LANGUAGE DeriveGeneric #-}
-{-# LANGUAGE DeriveTraversable #-}
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE GADTs #-}
-{-# LANGUAGE GeneralizedNewtypeDeriving #-}
-{-# LANGUAGE OverloadedStrings #-}
-{-# LANGUAGE RecordWildCards #-}
-{-# LANGUAGE ScopedTypeVariables #-}
-{-# LANGUAGE StandaloneDeriving #-}
-{-# LANGUAGE TemplateHaskell #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE UndecidableInstances #-}
+{-# OPTIONS_GHC -Wno-orphans #-}
 module Data.OpenApi.Internal where
 
 import Prelude ()
@@ -45,8 +31,8 @@ import           Network.HTTP.Media    (MediaType, mainType, parameters, parseAc
                                         (/:))
 import           Text.Read             (readMaybe)
 
-import           Data.HashMap.Strict.InsOrd (InsOrdHashMap)
-import qualified Data.HashMap.Strict.InsOrd as InsOrdHashMap
+import           Data.HashMap.Strict.InsOrd.Compat (InsOrdHashMap)
+import qualified Data.HashMap.Strict.InsOrd.Compat as InsOrdHashMap
 
 import Data.OpenApi.Aeson.Compat        (deleteKey)
 import Data.OpenApi.Internal.AesonUtils (AesonDefaultValue (..), HasSwaggerAesonOptions (..),
@@ -335,7 +321,10 @@ instance Data MediaType where
 
   dataTypeOf _ = mediaTypeData
 
+mediaTypeConstr :: Constr
 mediaTypeConstr = mkConstr mediaTypeData "MediaType" [] Prefix
+
+mediaTypeData :: DataType
 mediaTypeData = mkDataType "MediaType" [mediaTypeConstr]
 
 instance Hashable MediaType where
@@ -1006,12 +995,12 @@ deriveGeneric ''OpenApiSpecVersion
 -- =======================================================================
 
 instance Semigroup OpenApiSpecVersion where
-  (<>) (OpenApiSpecVersion a) (OpenApiSpecVersion b) = OpenApiSpecVersion $ max a b 
-  
+  (<>) (OpenApiSpecVersion a) (OpenApiSpecVersion b) = OpenApiSpecVersion $ max a b
+
 instance Monoid OpenApiSpecVersion where
   mempty = OpenApiSpecVersion (makeVersion [3,0,0])
   mappend = (<>)
-  
+
 instance Semigroup OpenApi where
   (<>) = genericMappend
 instance Monoid OpenApi where
@@ -1282,7 +1271,7 @@ instance FromJSON OAuth2AuthorizationCodeFlow where
 -- Manual ToJSON instances
 -- =======================================================================
 
-instance ToJSON OpenApiSpecVersion where 
+instance ToJSON OpenApiSpecVersion where
   toJSON (OpenApiSpecVersion v)= toJSON . showVersion $ v
 
 instance ToJSON MediaType where
@@ -1456,15 +1445,15 @@ instance FromJSON OpenApiSpecVersion where
   parseJSON = withText "OpenApiSpecVersion" $ \str ->
             let validatedVersion :: Either String Version
                 validatedVersion = do
-                  parsedVersion <- readVersion str 
+                  parsedVersion <- readVersion str
                   unless ((parsedVersion >= lowerOpenApiSpecVersion) && (parsedVersion <= upperOpenApiSpecVersion)) $
                      Left ("The provided version " <> showVersion parsedVersion <> " is out of the allowed range >=" <> showVersion lowerOpenApiSpecVersion <> " && <=" <> showVersion upperOpenApiSpecVersion)
                   return parsedVersion
-             in 
+             in
               either fail (return . OpenApiSpecVersion) validatedVersion
     where
     readVersion :: Text -> Either String Version
-    readVersion v = case readP_to_S parseVersion (Text.unpack v) of 
+    readVersion v = case readP_to_S parseVersion (Text.unpack v) of
       [] -> Left $ "Failed to parse as a version string " <> Text.unpack v
       solutions -> Right (fst . last $ solutions)
 
@@ -1649,7 +1638,7 @@ instance HasSwaggerAesonOptions Encoding where
 instance HasSwaggerAesonOptions Link where
   swaggerAesonOptions _ = mkSwaggerAesonOptions "link"
 
-instance AesonDefaultValue Version where 
+instance AesonDefaultValue Version where
   defaultValue = Just (makeVersion [3,0,0])
 instance AesonDefaultValue OpenApiSpecVersion
 instance AesonDefaultValue Server
diff --git a/src/Data/OpenApi/Internal/AesonUtils.hs b/src/Data/OpenApi/Internal/AesonUtils.hs
index 3804ab32..2b1e2625 100644
--- a/src/Data/OpenApi/Internal/AesonUtils.hs
+++ b/src/Data/OpenApi/Internal/AesonUtils.hs
@@ -1,10 +1,3 @@
-{-# LANGUAGE DataKinds #-}
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE GADTs #-}
-{-# LANGUAGE ScopedTypeVariables #-}
-{-# LANGUAGE ExplicitForAll #-}
-{-# LANGUAGE TemplateHaskell #-}
-{-# LANGUAGE UndecidableSuperClasses #-}
 module Data.OpenApi.Internal.AesonUtils (
     -- * Generic functions
     AesonDefaultValue(..),
@@ -37,7 +30,7 @@ import Generics.SOP
 
 import qualified Data.Text as T
 import qualified Data.Set as Set
-import qualified Data.HashMap.Strict.InsOrd as InsOrd
+import qualified Data.HashMap.Strict.InsOrd.Compat as InsOrd
 import qualified Data.HashSet.InsOrd as InsOrdHS
 
 import Data.OpenApi.Aeson.Compat (keyToString, objectToList, stringToKey)
diff --git a/src/Data/OpenApi/Internal/ParamSchema.hs b/src/Data/OpenApi/Internal/ParamSchema.hs
index 75b637a2..ae83e0c5 100644
--- a/src/Data/OpenApi/Internal/ParamSchema.hs
+++ b/src/Data/OpenApi/Internal/ParamSchema.hs
@@ -1,16 +1,3 @@
-{-# LANGUAGE DataKinds #-}
-{-# LANGUAGE DefaultSignatures #-}
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE KindSignatures #-}
-{-# LANGUAGE OverloadedStrings #-}
-{-# LANGUAGE PackageImports #-}
-{-# LANGUAGE PolyKinds #-}
-{-# LANGUAGE ScopedTypeVariables #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE TypeOperators #-}
-{-# LANGUAGE TypeSynonymInstances #-}
-{-# LANGUAGE UndecidableInstances #-}
 -- Generic a is redundant in  ToParamSchema a default imple
 {-# OPTIONS_GHC -Wno-redundant-constraints #-}
 -- For TypeErrors
@@ -19,6 +6,7 @@ module Data.OpenApi.Internal.ParamSchema where
 
 import Control.Lens
 import Data.Aeson (ToJSON (..))
+import Data.Kind (Type)
 import Data.Proxy
 import GHC.Generics
 
@@ -313,7 +301,7 @@ instance ToParamSchema UUID where
 genericToParamSchema :: forall a t. (Generic a, GToParamSchema (Rep a)) => SchemaOptions -> Proxy a -> Schema
 genericToParamSchema opts _ = gtoParamSchema opts (Proxy :: Proxy (Rep a)) mempty
 
-class GToParamSchema (f :: * -> *) where
+class GToParamSchema (f :: Type -> Type) where
   gtoParamSchema :: SchemaOptions -> Proxy f -> Schema -> Schema
 
 instance GToParamSchema f => GToParamSchema (D1 d f) where
@@ -331,7 +319,7 @@ instance ToParamSchema c => GToParamSchema (K1 i c) where
 instance (GEnumParamSchema f, GEnumParamSchema g) => GToParamSchema (f :+: g) where
   gtoParamSchema opts _ = genumParamSchema opts (Proxy :: Proxy (f :+: g))
 
-class GEnumParamSchema (f :: * -> *) where
+class GEnumParamSchema (f :: Type -> Type) where
   genumParamSchema :: SchemaOptions -> Proxy f -> Schema -> Schema
 
 instance (GEnumParamSchema f, GEnumParamSchema g) => GEnumParamSchema (f :+: g) where
diff --git a/src/Data/OpenApi/Internal/Schema.hs b/src/Data/OpenApi/Internal/Schema.hs
index da56acf0..e5fa09d1 100644
--- a/src/Data/OpenApi/Internal/Schema.hs
+++ b/src/Data/OpenApi/Internal/Schema.hs
@@ -1,21 +1,5 @@
 {-# LANGUAGE CPP #-}
-{-# LANGUAGE ConstraintKinds #-}
-{-# LANGUAGE DataKinds #-}
-{-# LANGUAGE DefaultSignatures #-}
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE KindSignatures #-}
 {-# LANGUAGE OverloadedLists #-}
-{-# LANGUAGE OverloadedStrings #-}
-{-# LANGUAGE PackageImports #-}
-{-# LANGUAGE PolyKinds #-}
-{-# LANGUAGE ScopedTypeVariables #-}
-{-# LANGUAGE TupleSections #-}
-{-# LANGUAGE TypeApplications #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE TypeOperators #-}
-{-# LANGUAGE TypeSynonymInstances #-}
-{-# LANGUAGE UndecidableInstances #-}
 {-# OPTIONS_GHC -Wno-redundant-constraints #-}
 -- For TypeErrors
 {-# OPTIONS_GHC -Wno-unticked-promoted-constructors #-}
@@ -24,6 +8,8 @@ module Data.OpenApi.Internal.Schema where
 import Prelude ()
 import Prelude.Compat
 
+import Data.Kind (Type)
+
 import Control.Lens hiding (allOf)
 import Data.Data.Lens (template)
 
@@ -39,7 +25,7 @@ import Data.HashMap.Strict (HashMap)
 import qualified Data.HashMap.Strict as HashMap
 import           "unordered-containers" Data.HashSet (HashSet)
 import qualified "unordered-containers" Data.HashSet as HashSet
-import qualified Data.HashMap.Strict.InsOrd as InsOrdHashMap
+import qualified Data.HashMap.Strict.InsOrd.Compat as InsOrdHashMap
 import Data.Int
 import Data.IntSet (IntSet)
 import Data.IntMap (IntMap)
@@ -587,7 +573,7 @@ sketchStrictSchema = go . toJSON
       where
         names = objectKeys o
 
-class GToSchema (f :: * -> *) where
+class GToSchema (f :: Type -> Type) where
   gdeclareNamedSchema :: SchemaOptions -> Proxy f -> Schema -> Declare (Definitions Schema) NamedSchema
 
 instance {-# OVERLAPPABLE #-} ToSchema a => ToSchema [a] where
@@ -1046,7 +1032,7 @@ gdeclareNamedSumSchema opts proxy _
 
 type AllNullary = All
 
-class GSumToSchema (f :: * -> *)  where
+class GSumToSchema (f :: Type -> Type)  where
   gsumToSchema :: SchemaOptions -> Proxy f -> WriterT AllNullary (Declare (Definitions Schema)) [(T.Text, Referenced Schema)]
 
 instance (GSumToSchema f, GSumToSchema g) => GSumToSchema (f :+: g) where
diff --git a/src/Data/OpenApi/Internal/Schema/Validation.hs b/src/Data/OpenApi/Internal/Schema/Validation.hs
index 5554ccf8..42340145 100644
--- a/src/Data/OpenApi/Internal/Schema/Validation.hs
+++ b/src/Data/OpenApi/Internal/Schema/Validation.hs
@@ -1,19 +1,5 @@
 {-# OPTIONS_GHC -Wall                  #-}
 {-# LANGUAGE CPP                        #-}
-{-# LANGUAGE DataKinds                  #-}
-{-# LANGUAGE DeriveFunctor              #-}
-{-# LANGUAGE FlexibleInstances          #-}
-{-# LANGUAGE FunctionalDependencies     #-}
-{-# LANGUAGE GADTs                      #-}
-{-# LANGUAGE GeneralizedNewtypeDeriving #-}
-{-# LANGUAGE LambdaCase                 #-}
-{-# LANGUAGE MultiParamTypeClasses      #-}
-{-# LANGUAGE PackageImports             #-}
-{-# LANGUAGE RankNTypes                 #-}
-{-# LANGUAGE ScopedTypeVariables        #-}
-{-# LANGUAGE TemplateHaskell            #-}
-{-# LANGUAGE UndecidableInstances       #-}
-{-# LANGUAGE ViewPatterns               #-}
 -- |
 -- Module:      Data.OpenApi.Internal.Schema.Validation
 -- Copyright:   (c) 2015 GetShopTV
@@ -40,7 +26,7 @@ import           Data.Foldable                       (for_, sequenceA_,
 #if !MIN_VERSION_aeson(2,0,0)
 import           Data.HashMap.Strict                 (HashMap)
 #endif
-import qualified Data.HashMap.Strict.InsOrd          as InsOrdHashMap
+import qualified Data.HashMap.Strict.InsOrd.Compat   as InsOrdHashMap
 import qualified "unordered-containers" Data.HashSet as HashSet
 import           Data.Maybe                          (fromMaybe)
 import           Data.Proxy
diff --git a/src/Data/OpenApi/Internal/TypeShape.hs b/src/Data/OpenApi/Internal/TypeShape.hs
index 89230e21..8af73b1b 100644
--- a/src/Data/OpenApi/Internal/TypeShape.hs
+++ b/src/Data/OpenApi/Internal/TypeShape.hs
@@ -1,11 +1,7 @@
-{-# LANGUAGE ConstraintKinds #-}
-{-# LANGUAGE DataKinds #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE TypeOperators #-}
-{-# LANGUAGE UndecidableInstances #-}
 
 module Data.OpenApi.Internal.TypeShape where
 
+import Data.Kind (Type)
 import Data.Proxy
 import GHC.Generics
 import GHC.TypeLits
@@ -46,7 +42,7 @@ type family GenericHasSimpleShape t (f :: Symbol) (s :: TypeShape) :: Constraint
       )
 
 -- | Infer a 'TypeShape' for a generic representation of a type.
-type family GenericShape (g :: * -> *) :: TypeShape
+type family GenericShape (g :: Type -> Type) :: TypeShape
 
 type instance GenericShape (f :*: g)        = ProdCombine  (GenericShape f) (GenericShape g)
 type instance GenericShape (f :+: g)        = SumCombine   (GenericShape f) (GenericShape g)
diff --git a/src/Data/OpenApi/Internal/Utils.hs b/src/Data/OpenApi/Internal/Utils.hs
index 8bcdd3b1..a8aaa3ae 100644
--- a/src/Data/OpenApi/Internal/Utils.hs
+++ b/src/Data/OpenApi/Internal/Utils.hs
@@ -1,9 +1,3 @@
-{-# LANGUAGE DefaultSignatures #-}
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE OverloadedStrings #-}
-{-# LANGUAGE RankNTypes #-}
-{-# LANGUAGE TypeOperators #-}
 module Data.OpenApi.Internal.Utils where
 
 import Prelude ()
@@ -20,8 +14,8 @@ import Data.Data
 import Data.Hashable (Hashable)
 import Data.HashMap.Strict (HashMap)
 import qualified Data.HashMap.Strict as HashMap
-import Data.HashMap.Strict.InsOrd (InsOrdHashMap)
-import qualified Data.HashMap.Strict.InsOrd as InsOrdHashMap
+import Data.HashMap.Strict.InsOrd.Compat (InsOrdHashMap)
+import qualified Data.HashMap.Strict.InsOrd.Compat as InsOrdHashMap
 import Data.Map (Map)
 import Data.Set (Set)
 import Data.Text (Text)
diff --git a/src/Data/OpenApi/Lens.hs b/src/Data/OpenApi/Lens.hs
index b8e23101..f3e6f30f 100644
--- a/src/Data/OpenApi/Lens.hs
+++ b/src/Data/OpenApi/Lens.hs
@@ -1,13 +1,3 @@
-{-# LANGUAGE FlexibleContexts #-}
-{-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE FunctionalDependencies #-}
-{-# LANGUAGE GADTs #-}
-{-# LANGUAGE MultiParamTypeClasses #-}
-{-# LANGUAGE RankNTypes #-}
-{-# LANGUAGE TemplateHaskell #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE DataKinds #-}
-{-# LANGUAGE UndecidableInstances #-}
 {-# OPTIONS_GHC -fno-warn-orphans #-}
 -- |
 -- Module:      Data.OpenApi.Lens
diff --git a/src/Data/OpenApi/Operation.hs b/src/Data/OpenApi/Operation.hs
index cb8a07e0..845271ad 100644
--- a/src/Data/OpenApi/Operation.hs
+++ b/src/Data/OpenApi/Operation.hs
@@ -1,4 +1,3 @@
-{-# LANGUAGE RankNTypes #-}
 -- |
 -- Module:      Data.OpenApi.Operation
 -- Maintainer:  Nickolay Kudasov <nickolay@getshoptv.com>
@@ -47,7 +46,7 @@ import Data.OpenApi.Internal
 import Data.OpenApi.Lens
 import Data.OpenApi.Schema
 
-import qualified Data.HashMap.Strict.InsOrd as InsOrdHashMap
+import qualified Data.HashMap.Strict.InsOrd.Compat as InsOrdHashMap
 import qualified Data.HashSet.InsOrd as InsOrdHS
 
 -- $setup
@@ -55,7 +54,7 @@ import qualified Data.HashSet.InsOrd as InsOrdHS
 -- >>> import Data.Proxy
 -- >>> import Data.Time
 -- >>> import qualified Data.ByteString.Lazy.Char8 as BSL
--- >>> import qualified Data.HashMap.Strict.InsOrd as IOHM
+-- >>> import qualified Data.HashMap.Strict.InsOrd.Compat as IOHM
 -- >>> import Data.OpenApi.Internal.Utils
 
 -- | Prepend path piece to all operations of the spec.
diff --git a/src/Data/OpenApi/Optics.hs b/src/Data/OpenApi/Optics.hs
index 3d0a42e8..8f71454e 100644
--- a/src/Data/OpenApi/Optics.hs
+++ b/src/Data/OpenApi/Optics.hs
@@ -1,10 +1,3 @@
-{-# LANGUAGE DataKinds #-}
-{-# LANGUAGE FlexibleInstances #-}
-{-# LANGUAGE MultiParamTypeClasses #-}
-{-# LANGUAGE OverloadedLabels #-}
-{-# LANGUAGE TemplateHaskell #-}
-{-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE UndecidableInstances #-}
 {-# OPTIONS_GHC -fno-warn-orphans #-}
 -- |
 -- Module:      Data.OpenApi.Optics
@@ -18,7 +11,7 @@
 -- >>> import Optics.Core
 -- >>> :set -XOverloadedLabels
 -- >>> import qualified Data.ByteString.Lazy.Char8 as BSL
--- >>> import qualified Data.HashMap.Strict.InsOrd as IOHM
+-- >>> import qualified Data.HashMap.Strict.InsOrd.Compat as IOHM
 --
 -- Example from the "Data.OpenApi" module using @optics@:
 --
diff --git a/src/Data/OpenApi/Schema/Generator.hs b/src/Data/OpenApi/Schema/Generator.hs
index 9cb4014f..8ccaf574 100644
--- a/src/Data/OpenApi/Schema/Generator.hs
+++ b/src/Data/OpenApi/Schema/Generator.hs
@@ -1,6 +1,4 @@
-{-# LANGUAGE GADTs               #-}
-{-# LANGUAGE OverloadedLists     #-}
-{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE OverloadedLists #-}
 
 module Data.OpenApi.Schema.Generator where
 
@@ -11,7 +9,7 @@ import           Control.Lens.Operators
 import           Control.Monad                           (filterM)
 import           Data.Aeson
 import           Data.Aeson.Types
-import qualified Data.HashMap.Strict.InsOrd              as M
+import qualified Data.HashMap.Strict.InsOrd.Compat       as M
 import           Data.Maybe
 import           Data.Proxy
 import           Data.Scientific
@@ -70,6 +68,7 @@ schemaGen defns schema =
               OpenApiItemsArray refs ->
                   let itemGens = schemaGen defns . dereference defns <$> refs
                   in fmap (Array . V.fromList) $ sequence itemGens
+        | otherwise -> pure $ Array V.empty
       Just OpenApiString -> do
         size <- getSize
         let minLength' = fromMaybe 0 $ fromInteger <$> schema ^. minLength
diff --git a/src/Data/OpenApi/SchemaOptions.hs b/src/Data/OpenApi/SchemaOptions.hs
index ed95881f..8d920cd3 100644
--- a/src/Data/OpenApi/SchemaOptions.hs
+++ b/src/Data/OpenApi/SchemaOptions.hs
@@ -1,4 +1,3 @@
-{-# LANGUAGE RecordWildCards #-}
 -- |
 -- Module:      Data.OpenApi.SchemaOptions
 -- Maintainer:  Nickolay Kudasov <nickolay@getshoptv.com>
diff --git a/test/Data/OpenApi/SchemaSpec.hs b/test/Data/OpenApi/SchemaSpec.hs
index 0a3f96e7..a2986921 100644
--- a/test/Data/OpenApi/SchemaSpec.hs
+++ b/test/Data/OpenApi/SchemaSpec.hs
@@ -9,7 +9,7 @@ import Prelude.Compat
 
 import Control.Lens ((^.))
 import Data.Aeson (Value)
-import qualified Data.HashMap.Strict.InsOrd as InsOrdHashMap
+import qualified Data.HashMap.Strict.InsOrd.Compat as InsOrdHashMap
 import Data.Proxy
 import Data.Set (Set)
 import qualified Data.Text as Text