diff --git a/.gitea/workflows/ci.yml b/.gitea/workflows/ci.yml
index 6179aa2..2dfd963 100644
--- a/.gitea/workflows/ci.yml
+++ b/.gitea/workflows/ci.yml
@@ -66,7 +66,14 @@ jobs:
       - name: go mod tidy is clean
         run: |
           go mod tidy
-          git diff --exit-code go.mod go.sum
+          # go.sum may not exist yet (no external deps), so don't name it as a
+          # diff path (git errors on a missing path). git status flags both a
+          # modified go.mod and a freshly-created untracked go.sum.
+          CHANGES=$(git status --porcelain -- go.mod go.sum)
+          if [ -n "$CHANGES" ]; then
+            echo "go.mod/go.sum not tidy:"; echo "$CHANGES"; git diff -- go.mod; exit 1
+          fi
+          echo "OK: go.mod/go.sum tidy."
 
       - name: Core stays majordomo+stdlib only
         run: |