diff --git a/src/Codec/Xlsx/Formatted.hs b/src/Codec/Xlsx/Formatted.hs
index ef2ce049..6fb9d45c 100644
--- a/src/Codec/Xlsx/Formatted.hs
+++ b/src/Codec/Xlsx/Formatted.hs
@@ -57,6 +57,7 @@ import Data.Tuple (swap)
 import GHC.Generics (Generic)
 import Prelude hiding (mapM)
 import Safe (headNote, fromJustNote)
+import Control.Monad (unless, guard, forM)
 
 import Codec.Xlsx.Types
 
diff --git a/src/Codec/Xlsx/Parser.hs b/src/Codec/Xlsx/Parser.hs
index 3b96659e..19567e9e 100644
--- a/src/Codec/Xlsx/Parser.hs
+++ b/src/Codec/Xlsx/Parser.hs
@@ -28,7 +28,7 @@ import Lens.Micro
 #else
 import Control.Lens hiding ((<.>), element, views)
 #endif
-import Control.Monad (join, void)
+import Control.Monad (join, void, liftM4)
 import Control.Monad.Except (catchError, throwError)
 import Data.Bool (bool)
 import Data.ByteString (ByteString)
@@ -45,7 +45,7 @@ import qualified Data.Text as T
 import Data.Traversable
 import GHC.Generics (Generic)
 import Prelude hiding (sequence)
-import Safe
+import Safe (headNote)
 import System.FilePath.Posix
 import Text.XML as X
 import Text.XML.Cursor hiding (bool)
@@ -112,11 +112,12 @@ toXlsxEitherBase parseSheet bs = do
   (wfs, names, cacheSources, dateBase) <- readWorkbook ar
   sheets <- forM wfs $ \wf -> do
       sheet <- parseSheet ar sst contentTypes cacheSources wf
-      return . (wfName wf,) . (wsState .~ wfState wf) $ sheet
+      return . (wfName wf,) . (wsSheetId .~ wfSheetId wf) . (wsState .~ wfState wf) $ sheet
   CustomProperties customPropMap <- getCustomProperties ar
   return $ Xlsx sheets (getStyles ar) names customPropMap dateBase
 
 data WorksheetFile = WorksheetFile { wfName :: Text
+                                   , wfSheetId :: Int
                                    , wfState :: SheetState
                                    , wfPath :: FilePath
                                    }
@@ -206,6 +207,7 @@ extractSheetFast ar sst contentTypes caches wf = do
             , _wsPivotTables = []
             , _wsTables = []
             , _wsState = wfState wf
+            , _wsSheetId = wfSheetId wf
             , ..
             }
             , tableIds
@@ -503,6 +505,7 @@ extractSheet ar sst contentTypes caches wf = do
       mProtection
       sharedFormulas
       (wfState wf)
+      (wfSheetId wf)
 
 extractCellValue :: SharedStringTable -> Text -> Cursor -> [CellValue]
 extractCellValue sst t cur
@@ -656,7 +659,7 @@ readWorkbook ar = do
   sheets <-
     sequence $
     cur $/ element (n_ "sheets") &/ element (n_ "sheet") >=>
-    liftA3 (worksheetFile wbPath wbRels) <$> attribute "name" <*> fromAttributeDef "state" def <*>
+    liftM4 (worksheetFile wbPath wbRels) <$> attribute "name" <*> fromAttribute "sheetId" <*> fromAttributeDef "state" def <*>
     fromAttribute (odr "id")
   let cacheRefs =
         cur $/ element (n_ "pivotCaches") &/ element (n_ "pivotCache") >=>
@@ -689,9 +692,9 @@ getTable ar fp = do
   cur <- xmlCursorRequired ar fp
   headErr (InvalidFile fp "Couldn't parse drawing") (fromCursor cur)
 
-worksheetFile :: FilePath -> Relationships -> Text -> SheetState -> RefId -> Parser WorksheetFile
-worksheetFile parentPath wbRels name visibility rId =
-  WorksheetFile name visibility <$> lookupRelPath parentPath wbRels rId
+worksheetFile :: FilePath -> Relationships -> Text -> Int -> SheetState -> RefId -> Parser WorksheetFile
+worksheetFile parentPath wbRels name sheetId visibility rId =
+  WorksheetFile name sheetId visibility <$> lookupRelPath parentPath wbRels rId
 
 getRels :: Zip.Archive -> FilePath -> Parser Relationships
 getRels ar fp = do
diff --git a/src/Codec/Xlsx/Parser/Stream.hs b/src/Codec/Xlsx/Parser/Stream.hs
index 4ee5cc78..d25a3be6 100644
--- a/src/Codec/Xlsx/Parser/Stream.hs
+++ b/src/Codec/Xlsx/Parser/Stream.hs
@@ -85,6 +85,7 @@ import Lens.Micro.TH
 import Control.Lens
 #endif
 import Codec.Xlsx.Parser.Internal
+import Control.Monad (when, void, unless)
 import Control.Monad.Catch
 import Control.Monad.Except
 import Control.Monad.Reader
diff --git a/src/Codec/Xlsx/Types.hs b/src/Codec/Xlsx/Types.hs
index 58c6dd7e..250e78f0 100644
--- a/src/Codec/Xlsx/Types.hs
+++ b/src/Codec/Xlsx/Types.hs
@@ -47,6 +47,7 @@ module Codec.Xlsx.Types (
     , wsProtection
     , wsSharedFormulas
     , wsState
+    , wsSheetId
     -- ** Cells
     , Cell.cellValue
     , Cell.cellStyle
@@ -284,6 +285,7 @@ data Worksheet = Worksheet
   , _wsProtection :: Maybe SheetProtection
   , _wsSharedFormulas :: Map SharedFormulaIndex SharedFormulaOptions
   , _wsState :: SheetState
+  , _wsSheetId :: Int
   } deriving (Eq, Show, Generic)
 instance NFData Worksheet
 
@@ -307,6 +309,7 @@ instance Default Worksheet where
     , _wsProtection = Nothing
     , _wsSharedFormulas = M.empty
     , _wsState = def
+    , _wsSheetId = 1
     }
 
 -- | Raw worksheet styles, for structured implementation see 'StyleSheet'
diff --git a/src/Codec/Xlsx/Writer/Stream.hs b/src/Codec/Xlsx/Writer/Stream.hs
index 0c10ea5c..11e1da9c 100644
--- a/src/Codec/Xlsx/Writer/Stream.hs
+++ b/src/Codec/Xlsx/Writer/Stream.hs
@@ -71,6 +71,7 @@ import Text.XML (toXMLElement)
 import qualified Text.XML as TXML
 import Text.XML.Stream.Render
 import Text.XML.Unresolved (elementToEvents)
+import Control.Monad (void, when, unless)
 
 
 upsertSharedStrings :: MonadState SharedStringState m => Row -> m [(Text,Int)]
@@ -264,7 +265,7 @@ writeSst sharedStrings' = doc (n_ "sst") $
                   ) $ sortBy (\(_, i) (_, y :: Int) -> compare i y) $ Map.toList sharedStrings'
 
 writeEvents ::  PrimMonad m => ConduitT Event Builder m ()
-writeEvents = renderBuilder (def {rsPretty=False})
+writeEvents = renderBuilder def
 
 sheetViews :: forall m . MonadReader SheetWriteSettings m => forall i . ConduitT i Event m ()
 sheetViews = do
diff --git a/test/TestXlsx.hs b/test/TestXlsx.hs
index 1ca4bb77..9fd4ce1a 100644
--- a/test/TestXlsx.hs
+++ b/test/TestXlsx.hs
@@ -40,12 +40,12 @@ testXlsx = Xlsx sheets minimalStyles definedNames customProperties DateBase1904
       , ("with pivot table", pvSheet)
       , ("cellrange DV source", foreignDvSourceSheet) -- "foreign" sheet holding validation data
       , ("cellrange DV test", foreignDvTestSheet) -- applies validation using foreign cell ranges
-      , ("hidden sheet", def & wsState .~ Hidden & cellValueAt (1,1) ?~ CellText "I'm hidden!")
-      , ("VERY hidden sheet", def & wsState .~ VeryHidden & cellValueAt (1,1) ?~ CellText "I'm VERY hidden!!")
+      , ("hidden sheet", def & wsState .~ Hidden & cellValueAt (1,1) ?~ CellText "I'm hidden!" & wsSheetId .~ 6)
+      , ("VERY hidden sheet", def & wsState .~ VeryHidden & cellValueAt (1,1) ?~ CellText "I'm VERY hidden!!" & wsSheetId .~ 7)
       ]
     sheet1 = Worksheet cols rowProps testCellMap1 drawing ranges
       sheetViews pageSetup cFormatting validations [] (Just autoFilter)
-      tables (Just protection) sharedFormulas def
+      tables (Just protection) sharedFormulas def 1
     sharedFormulas =
       M.fromList
         [ (SharedFormulaIndex 0, SharedFormulaOptions (CellRef "A5:C5") (Formula "A4"))
@@ -71,12 +71,13 @@ testXlsx = Xlsx sheets minimalStyles definedNames customProperties DateBase1904
       { _sprScenarios = False
       , _sprLegacyPassword = Just $ legacyPassword "hard password"
       }
-    sheet2 = def & wsCells .~ testCellMap2
-    foreignDvSourceSheet = def & wsCells .~ cellRangeDvSourceMap
+    sheet2 = def & wsCells .~ testCellMap2 & wsSheetId .~ 2
+    foreignDvSourceSheet = def & wsCells .~ cellRangeDvSourceMap & wsSheetId .~ 4
     foreignDvTestSheet = def &  wsDataValidations .~ foreignValidations &
                                 wsCells . at (1, 1) ?~
                                     (def & cellValue ?~ CellText ("Hi! try " <> unCellRef testForeignDvRange))
-    pvSheet = sheetWithPvCells & wsPivotTables .~ [testPivotTable]
+                                & wsSheetId .~ 5
+    pvSheet = sheetWithPvCells & wsPivotTables .~ [testPivotTable] & wsSheetId .~ 3
     sheetWithPvCells = def & wsCells .~ testPivotSrcCells
     rowProps = M.fromList [(1, RowProps { rowHeight       = Just (CustomHeight 50)
                                         , rowStyle        = Just 3