diff --git a/.github/scripts/check-contrib.sh b/.github/scripts/check-contrib.sh
new file mode 100755
index 000000000..3cc0ef321
--- /dev/null
+++ b/.github/scripts/check-contrib.sh
@@ -0,0 +1,8 @@
+#!/usr/bin/env sh
+set -eu
+
+bash --version
+zsh --version
+
+find contrib -type f \( -name '*.sh' -o -name '*.bash' \) -exec bash --norc -n {} \;
+find contrib/zsh_compl -type f -name '_rgb*' -exec zsh -n {} \;
diff --git a/contrib/checkdiff.bash b/.github/scripts/check-diff.bash
similarity index 100%
rename from contrib/checkdiff.bash
rename to .github/scripts/check-diff.bash
diff --git a/contrib/checkformat.sh b/.github/scripts/check-format.sh
similarity index 100%
rename from contrib/checkformat.sh
rename to .github/scripts/check-format.sh
diff --git a/.github/scripts/draft-release.sh b/.github/scripts/draft-release.sh
index 97fe2a024..c55d8a71c 100755
--- a/.github/scripts/draft-release.sh
+++ b/.github/scripts/draft-release.sh
@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 set -euo pipefail
 
 tag=$1
diff --git a/.github/scripts/install_deps.sh b/.github/scripts/install-deps.sh
similarity index 100%
rename from .github/scripts/install_deps.sh
rename to .github/scripts/install-deps.sh
diff --git a/.github/workflows/check-contrib.yml b/.github/workflows/check-contrib.yml
new file mode 100644
index 000000000..34e24620d
--- /dev/null
+++ b/.github/workflows/check-contrib.yml
@@ -0,0 +1,23 @@
+name: Contrib script syntax checking
+on:
+  - push
+  - pull_request
+
+env:
+  # Force colored output (see https://bixense.com/clicolors/ and https://force-color.org/)
+  TERM: xterm-256color
+  CLICOLOR: 1
+  CLICOLOR_FORCE: 1
+
+jobs:
+  check-contrib:
+    runs-on: ubuntu-slim
+    steps:
+      - name: Checkout repo
+        uses: actions/checkout@v7
+      - name: Install zsh
+        run: |
+          sudo apt install -Uyq zsh
+      - name: Check contrib scripts
+        run: |
+          .github/scripts/check-contrib.sh
diff --git a/.github/workflows/checkdiff.yml b/.github/workflows/check-diff.yml
similarity index 89%
rename from .github/workflows/checkdiff.yml
rename to .github/workflows/check-diff.yml
index 6dd92cf1a..1d1ef8740 100644
--- a/.github/workflows/checkdiff.yml
+++ b/.github/workflows/check-diff.yml
@@ -8,7 +8,7 @@ env:
   CLICOLOR_FORCE: 1
 
 jobs:
-  checkdiff:
+  check-diff:
     runs-on: ubuntu-slim
     steps:
       - name: Clone repo
@@ -20,7 +20,7 @@ jobs:
         run: |
           MERGE_BASE=$(gh api "/repos/{owner}/{repo}/compare/$BASE_SHA...$HEAD_SHA" --jq '.merge_base_commit.sha')
           git fetch origin "$MERGE_BASE"
-          contrib/checkdiff.bash "$MERGE_BASE" | sed -E 's/^/::warning::/'
+          .github/scripts/check-diff.bash "$MERGE_BASE" | sed -E 's/^/::warning::/'
         env:
           BASE_SHA: ${{ github.event.pull_request.base.sha }}
           HEAD_SHA: ${{ github.event.pull_request.head.sha }}
diff --git a/.github/workflows/checkformat.yml b/.github/workflows/check-format.yml
similarity index 88%
rename from .github/workflows/checkformat.yml
rename to .github/workflows/check-format.yml
index 65842b2a8..ccd56ccd1 100644
--- a/.github/workflows/checkformat.yml
+++ b/.github/workflows/check-format.yml
@@ -8,7 +8,7 @@ env:
   CLICOLOR_FORCE: 1
 
 jobs:
-  checkformat:
+  check-format:
     runs-on: ubuntu-slim
     steps:
       - name: Checkout repo
@@ -18,4 +18,4 @@ jobs:
           sudo apt install -Uyq clang-format
       - name: Check format
         run: |
-          contrib/checkformat.sh
+          .github/scripts/check-format.sh
diff --git a/.github/workflows/coverage.yml b/.github/workflows/coverage.yml
index 7a525dff4..f112cf27d 100644
--- a/.github/workflows/coverage.yml
+++ b/.github/workflows/coverage.yml
@@ -17,7 +17,7 @@ jobs:
         uses: actions/checkout@v7
       - name: Install deps
         run: |
-          .github/scripts/install_deps.sh ubuntu-latest lcov
+          .github/scripts/install-deps.sh ubuntu-latest lcov
       - name: Generate coverage report
         run: |
           contrib/coverage.bash --os ubuntu-latest --jobs "$(getconf _NPROCESSORS_ONLN)"
diff --git a/.github/workflows/create-release-artifacts.yml b/.github/workflows/create-release-artifacts.yml
index d24027f09..ee13a0bf9 100644
--- a/.github/workflows/create-release-artifacts.yml
+++ b/.github/workflows/create-release-artifacts.yml
@@ -33,7 +33,7 @@ jobs:
         uses: actions/checkout@v7
       - name: Install deps
         run: |
-          bash .github/scripts/install_deps.sh windows
+          bash .github/scripts/install-deps.sh windows
       - name: Build Windows binaries
         shell: cmd
         run: |
@@ -58,7 +58,7 @@ jobs:
         uses: actions/checkout@v7
       - name: Install deps
         run: |
-          ./.github/scripts/install_deps.sh macos lld
+          ./.github/scripts/install-deps.sh macos lld
       - name: Build binaries
         run: |
           cmake -B build -G Ninja --preset macos-static -DFETCHCONTENT_BASE_DIR="${{ env.DEPS_ROOT_DIR }}"
@@ -86,7 +86,7 @@ jobs:
         uses: actions/checkout@v7
       - name: Install deps
         run: |
-          ./.github/scripts/install_deps.sh ubuntu-22.04
+          ./.github/scripts/install-deps.sh ubuntu-22.04
       - name: Build binaries
         run: |
           make -k -j "$(getconf _NPROCESSORS_ONLN)" WARNFLAGS="-Wall -Wextra -pedantic -static" PKG_CONFIG="pkg-config --static" Q=
diff --git a/.github/workflows/testing.yml b/.github/workflows/testing.yml
index 33012cc19..523c95f56 100644
--- a/.github/workflows/testing.yml
+++ b/.github/workflows/testing.yml
@@ -52,7 +52,7 @@ jobs:
         uses: actions/checkout@v7
       - name: Install deps
         run: |
-          .github/scripts/install_deps.sh ${{ matrix.os }} ${{ matrix.cxx }}
+          .github/scripts/install-deps.sh ${{ matrix.os }} ${{ matrix.cxx }}
       - name: Build using Make
         if: matrix.buildsys == 'make'
         run: |
@@ -123,7 +123,7 @@ jobs:
         uses: actions/checkout@v7
       - name: Install deps
         run: |
-          .github/scripts/install_deps.sh macos lld
+          .github/scripts/install-deps.sh macos lld
       - name: Cache library deps
         uses: actions/cache@v5
         with:
@@ -185,7 +185,7 @@ jobs:
         uses: actions/checkout@v7
       - name: Install deps
         run: |
-          bash .github/scripts/install_deps.sh ${{ matrix.os }}
+          bash .github/scripts/install-deps.sh ${{ matrix.os }}
       - name: Cache library deps
         uses: actions/cache@v5
         with:
@@ -247,7 +247,7 @@ jobs:
         uses: actions/checkout@v7
       - name: Install deps
         run: |
-          .github/scripts/install_deps.sh ubuntu mingw${{ matrix.bits }}
+          .github/scripts/install-deps.sh ubuntu mingw${{ matrix.bits }}
       - name: Cache library deps
         uses: actions/cache@v5
         with:
@@ -292,7 +292,7 @@ jobs:
         uses: actions/checkout@v7
       - name: Install test deps
         run: |
-          .github/scripts/install_deps.sh windowsmingw
+          .github/scripts/install-deps.sh windowsmingw
       - name: Retrieve binaries
         uses: actions/download-artifact@v8
         with:
@@ -396,7 +396,7 @@ jobs:
           release: "14.3"
           usesh: true
           prepare: |
-            .github/scripts/install_deps.sh freebsd
+            .github/scripts/install-deps.sh freebsd
           run: | # Leak detection is not supported on FreeBSD, so disable it.
             cmake -B build --preset develop
             cmake --build build --verbose -- -k -j "$(getconf _NPROCESSORS_ONLN)"
diff --git a/Dockerfile b/Dockerfile
index bf070f58f..fb1461ec1 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -5,11 +5,12 @@ WORKDIR /rgbds
 
 COPY . .
 
+# Install dependencies
 RUN apt-get update && \
     apt-get install sudo make cmake gcc build-essential -y
+RUN ./.github/scripts/install-deps.sh debian
 
-# Install dependencies and compile RGBDS
-RUN ./.github/scripts/install_deps.sh debian
+# Build RGBDS
 RUN make -j "$(getconf _NPROCESSORS_ONLN)" CXXFLAGS="-O3 -flto -DNDEBUG -static" PKG_CONFIG="pkg-config --static" Q=
 
 # Create the install script
diff --git a/Makefile b/Makefile
index 5e3ec98c7..6f70ab8db 100644
--- a/Makefile
+++ b/Makefile
@@ -3,7 +3,7 @@
 .SUFFIXES:
 .SUFFIXES: .cpp .y .o
 
-.PHONY: all clean install checkdiff develop debug profile coverage format tidy iwyu wine-shim dist
+.PHONY: all clean install develop debug profile coverage format tidy iwyu wine-shim dist
 
 # User-defined variables
 
@@ -44,9 +44,6 @@ BISON := src/bison.sh
 
 RM := rm -rf
 
-# Used for checking pull requests
-BASE_REF := origin/master
-
 # Rules to build the RGBDS binaries
 
 all: rgbasm rgblink rgbfix rgbgfx
@@ -214,10 +211,6 @@ install: all
 	$Qinstall -m ${MANMODE} ${MANSRC}rgbds.5 ${MANSRC}rgbasm.5 ${MANSRC}rgbasm-old.5 ${MANSRC}rgblink.5 ${DESTDIR}${mandir}/man5/
 	$Qinstall -m ${MANMODE} ${MANSRC}rgbds.7 ${MANSRC}gbz80.7 ${DESTDIR}${mandir}/man7/
 
-# Target used to check for suspiciously missing changed files.
-checkdiff:
-	$Qcontrib/checkdiff.bash `git merge-base HEAD ${BASE_REF}`
-
 # Target used in development to prevent adding new issues to the source code.
 # All warnings are treated as errors to block the compilation and make the
 # continous integration infrastructure return failure.
diff --git a/contrib/coverage.bash b/contrib/coverage.bash
index fbf03fd41..b0c9ad294 100755
--- a/contrib/coverage.bash
+++ b/contrib/coverage.bash
@@ -1,5 +1,5 @@
 #!/usr/bin/env bash
-set -e
+set -eu
 
 usage() {
 	cat <<"EOF"
diff --git a/contrib/view_palettes.sh b/contrib/view_palettes.sh
index ef57951d0..f27ebf244 100755
--- a/contrib/view_palettes.sh
+++ b/contrib/view_palettes.sh
@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/usr/bin/env bash
 set -euo pipefail
 
 if [[ $# -ne 2 ]]; then