diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index bc2df1b0c1fd1d7f22a175daa47af54fd2e98ffe..fc3b7172570742ccd6744621eada44651585875f 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -622,7 +622,7 @@ sanity:
     - cd ${CI_PROJECT_DIR}/Python  # change into the Python directory
     - pip install --user -e '.[test]'  # install the package + test deps
     - python -m mypy corsika
-    - python -m isort --atomic corsika tests
+    - python -m isort --atomic --check-only corsika tests
     - python -m black -t py37 corsika tests
     - python -m flake8 corsika tests
     - python -m pytest --cov=corsika tests