diff --git a/.github/workflows/ci-tests.yml b/.github/workflows/ci-tests.yml
index 2f9c635c..5d70b568 100644
--- a/.github/workflows/ci-tests.yml
+++ b/.github/workflows/ci-tests.yml
@@ -110,7 +110,7 @@ jobs:
               working-directory: Nominatim
 
             - name: Python static typechecking
-              run: mypy nominatim
+              run: mypy --strict nominatim
               working-directory: Nominatim