diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 5884dc1..4c252f9 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -13,6 +13,7 @@ jobs:
       - uses: fabasoad/setup-prolog-action@v1
       - run: npm ci
       - run: npm test
+      - run: if [[ `git status --porcelain` ]]; then git status --porcelain && exit 1; fi
   lint:
     runs-on: ubuntu-latest
     steps: