diff --git a/.flake8 b/.flake8
index 48cf7d7..5890202 100644
--- a/.flake8
+++ b/.flake8
@@ -1,6 +1,6 @@
 [flake8]
 max-line-length = 127
 exclude = .git,__pycache__,doc/,docs/,build/,dist/,archive/,setup.py
-ignore = E121,E123,E126,E226,E24,E704,W503,W504,C901
+ignore = E121,E123,E126,E226,E24,E704,W292,W503,W504,C901
 per-file-ignores =
   __init__.py:F401
diff --git a/.github/workflows/python-package.yml b/.github/workflows/python-package.yml
index b8292b8..3da834f 100644
--- a/.github/workflows/python-package.yml
+++ b/.github/workflows/python-package.yml
@@ -34,7 +34,17 @@ jobs:
         pip install -e .[r_wrapper,tests,docs]
     - name: Lint with flake8
       run: |
-        flake8 . --count --statistics
+        # stop the build if there are Python syntax errors or undefined names
+        #    E9: Runtime errors (syntax, indentation, io)
+        #    F63: Wrong use of operators and always-true assertion tests
+        #    F7: Wrong position of statements (break, continue, return, ...)
+        #    F82: Undefined (variable) name
+        flake8 . --count --select=E9,F63,F7,F82 --show-source --statistics
+        #
+        # print warnings if other style errors are found.
+        #    see .flake8 config file for selected/ignored rules.
+        #    warnings can be found in the action logs
+        flake8 . --count --exit-zero --statistics --show-source
     - name: Test with pytest and measure coverage
       run: |
         pytest cblearn --cov=cblearn --cov-report=xml
diff --git a/cblearn/embedding/tests/test_sklearn_estimator_checks.py b/cblearn/embedding/tests/test_sklearn_estimator_checks.py
index e0ad992..26b737f 100644
--- a/cblearn/embedding/tests/test_sklearn_estimator_checks.py
+++ b/cblearn/embedding/tests/test_sklearn_estimator_checks.py
@@ -75,6 +75,7 @@ def wrap_triplet_estimator(estimator):
     'check_methods_sample_order_invariance',
 ]
 
+
 @pytest.mark.sklearn
 @parametrize_with_checks(
     ALL_TRIPLET_EMBEDDING_ESTIMATORS