diff --git a/tools/ci-changed-builds.sh b/tools/ci-changed-builds.sh
index df7f50c0..192fa228 100755
--- a/tools/ci-changed-builds.sh
+++ b/tools/ci-changed-builds.sh
@@ -1,7 +1,7 @@
 #!/bin/bash
 set -euo pipefail
 IFS=$'\n'
-filenames="$(git diff-tree -r --no-commit-id --name-status "$1" HEAD | ( grep -P '^[AM]\t(xep-[0-9]{4}|inbox/[^/]+)\.xml$' || true) | cut -f2)"
+filenames="$(git diff-tree -r --no-commit-id --name-status "$(git merge-base "$1" HEAD)" HEAD | ( grep -P '^[AM]\t(xep-[0-9]{4}|inbox/[^/]+)\.xml$' || true) | cut -f2)"
 if [ -z "$filenames" ]; then
     exit 0
 fi