diff --git a/contrib/heptapod-ci.yml b/contrib/heptapod-ci.yml
--- a/contrib/heptapod-ci.yml
+++ b/contrib/heptapod-ci.yml
@@ -5,6 +5,8 @@
 before_script:
     - hg clone . /tmp/mercurial-ci/ --noupdate
     - hg -R /tmp/mercurial-ci/ update `hg log --rev '.' --template '{node}'`
+    - cd /tmp/mercurial-ci/rust/rhg
+    - cargo build
     - cd /tmp/mercurial-ci/
     - ls -1 tests/test-check-*.* > /tmp/check-tests.txt