diff --git a/.github/workflows/build_linux.yml b/.github/workflows/build_linux.yml
index cbc88ef..17b365f 100644
--- a/.github/workflows/build_linux.yml
+++ b/.github/workflows/build_linux.yml
@@ -46,7 +46,9 @@ jobs:
         mvn dependency:copy -Dmaven.repo.local="build/download" \
               -Dartifact=io.github.ndsev:zserio:LATEST \
               -DoutputDirectory="build" -Dmdep.stripVersion=true
-        java -jar build/zserio.jar -java src tutorial.zs
+        java -jar build/zserio.jar -ignoreTimestamps -java src tutorial.zs
+        git add --intent-to-add src
+        git diff --exit-code -- src
         javac -d build -cp build/zserio-runtime.jar src/Main.java src/**/*.java
 
     - name: Test Zserio Java tutorial (sources regeneration)
diff --git a/.github/workflows/build_windows.yml b/.github/workflows/build_windows.yml
index 9310df4..7f4a6bc 100644
--- a/.github/workflows/build_windows.yml
+++ b/.github/workflows/build_windows.yml
@@ -48,7 +48,9 @@ jobs:
         mvn dependency:copy -Dmaven.repo.local="build/download" \
               -Dartifact=io.github.ndsev:zserio:LATEST \
               -DoutputDirectory="build" -Dmdep.stripVersion=true
-        java -jar build/zserio.jar -java src tutorial.zs
+        java -jar build/zserio.jar -ignoreTimestamps -java src tutorial.zs
+        git add --intent-to-add src
+        git diff --exit-code -- src
         javac -d build -cp build/zserio-runtime.jar src/Main.java src/**/*.java
       shell: bash