diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index c46a843..17a176d 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -141,13 +141,12 @@ jobs:
             echo "Promoting ${BASELINE} to stable release; current HEAD is a descendant."
             exit 0
           fi
-          if ! git merge-base --is-ancestor "${BASELINE}" HEAD; then
-            echo "ERROR: ${BASELINE} is not an ancestor of HEAD; select a Previous Release tag from this branch."
-            exit 1
-          fi
-          count="$(git rev-list --count "${BASELINE}..HEAD")"
-          if [ "$count" -eq 0 ]; then
-            echo "ERROR: No new commits since ${BASELINE}; refusing to create a duplicate release."
+          # BASELINE may not be a true git ancestor of HEAD (e.g. it was squash-merged
+          # into this branch's history rather than true-merged), so ancestry can't be
+          # relied on here. Compare tree content instead: if HEAD's tree is identical to
+          # BASELINE's, there's nothing new to release.
+          if [ "$(git rev-parse "${BASELINE}^{tree}")" = "$(git rev-parse "HEAD^{tree}")" ]; then
+            echo "ERROR: No changes since ${BASELINE} (working tree is identical); refusing to create a duplicate release."
             exit 1
           fi