diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index aeb629c3f..1f3194e7b 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -25,5 +25,10 @@ jobs:
       - name: Install dependencies
         run: npm install
 
+      - name: Build and check generated files
+        run: |
+          npm run build
+          script/check-generated-files
+
       - name: Test corpus & parse examples
         run: npm test
diff --git a/script/check-generated-files b/script/check-generated-files
new file mode 100755
index 000000000..dff20d01a
--- /dev/null
+++ b/script/check-generated-files
@@ -0,0 +1,13 @@
+#!/usr/bin/env bash
+
+set -eu
+
+if ! git diff-index --quiet HEAD -- {tsx,typescript}/src/; then
+    cat 1>&2 <<EOF
+Generated files in the working tree are inconsistent with HEAD.
+Make sure to commit generated files in {tsx,typescript}/src/ when the grammar changes.
+EOF
+    exit 1
+fi
+
+exit 0