diff --git a/contrib/heptapod-ci.yml b/contrib/heptapod-ci.yml
--- a/contrib/heptapod-ci.yml
+++ b/contrib/heptapod-ci.yml
@@ -20,6 +20,7 @@
       - cargo build
       - cd /tmp/mercurial-ci/
       - ls -1 tests/test-check-*.* > /tmp/check-tests.txt
+      - black --version
     script:
         - echo "python used, $PYTHON"
         - echo "$RUNTEST_ARGS"