ci: fix merge-mode
diff --git a/zuul.d/project.yaml b/zuul.d/project.yaml
index 50c47f1..a4a697b 100644
--- a/zuul.d/project.yaml
+++ b/zuul.d/project.yaml
@@ -13,7 +13,7 @@
 # under the License.
 
 - project:
-    merge-mode: squash
+    merge-mode: squash-merge
     check:
       jobs:
         - atmosphere-buildset-registry