diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index b5c44e793c727da9b6feba89fc0b3be3ecfb70c9..a660bb18f04bb9208ebb939e8cd5c7beddb1a029 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -119,6 +119,33 @@ build-package-source-builder-docker-image:
   variables:
     image: package-source-builder
 
+test-package-source-builder:
+  stage: image test
+  needs:
+    - build-package-source-builder-docker-image
+  image:
+    name: $CI_REGISTRY_IMAGE/${RELEASE}-package-source-builder:${TEST_TAG}
+    entrypoint: [ "" ]
+  script:
+    - git clone https://gitlab.apertis.org/infrastructure/test-data/fixture-dash-unmodified
+    - ": Verify we correctly detect when there are no local changes and use the co0 suffix"
+    - cd fixture-dash-unmodified
+    - apertis-pkg-merge-updates --package dash --upstream debian/buster --downstream apertis/v2020dev0
+    - git log --graph --oneline --decorate
+    - git diff debian/buster..
+    - test "$(dpkg-parsechangelog -SVersion)" = 0.5.10.2-5co0
+    - test "$(dpkg-parsechangelog -SDistribution)" = apertis
+    - cd ..
+    - git clone https://gitlab.apertis.org/infrastructure/test-data/fixture-dash-modified
+    - ": Verify we correctly detect local changes and do not finalise the changelog"
+    - cd fixture-dash-modified
+    - apertis-pkg-merge-updates --package dash --upstream debian/buster --downstream apertis/v2020dev0
+    - git log --graph --oneline --decorate
+    - git diff debian/buster..
+    - test "$(dpkg-parsechangelog -SVersion)" = 0.5.10.2-5co1
+    - test "$(dpkg-parsechangelog -SDistribution)" = UNRELEASED
+    - cd ..
+
 build-documentation-builder-docker-image:
   extends: .build-docker-image
   stage: derived images