diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 8d7d900ce5eb97c99a17be5262733d318660debc..b6b1cd80d36db7e3e0196a43d8621bf33e3ae967 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -411,4 +411,9 @@ default:
   variables:
     KUBERNETES_CPU_REQUEST: "2"
   script:
-    - git diff $CI_MERGE_REQUEST_TARGET_BRANCH_SHA --name-only | sed "s_^_../_" | yarn --cwd=./core run -s spellcheck:core --no-must-find-files --file-list stdin
+    - if [ -n "$CI_MERGE_REQUEST_TARGET_BRANCH_SHA" ]; then
+        echo "HEAD is $(git rev-parse HEAD). \$CI_MERGE_REQUEST_TARGET_BRANCH_SHA is ${CI_MERGE_REQUEST_TARGET_BRANCH_SHA}";
+      else
+        echo "HEAD is $(git rev-parse HEAD). \$CI_MERGE_REQUEST_DIFF_BASE_SHA is ${CI_MERGE_REQUEST_DIFF_BASE_SHA}";
+      fi;
+    - git diff ${CI_MERGE_REQUEST_TARGET_BRANCH_SHA:-$CI_MERGE_REQUEST_DIFF_BASE_SHA} --name-only | sed "s_^_../_" | yarn --cwd=./core run -s spellcheck:core --no-must-find-files --file-list stdin