diff --git a/script/static-checks/static-checks-check-copyright.sh b/script/static-checks/static-checks-check-copyright.sh
index 9027811..56d2e9d 100755
--- a/script/static-checks/static-checks-check-copyright.sh
+++ b/script/static-checks/static-checks-check-copyright.sh
@@ -20,7 +20,7 @@
 
 LOG_FILE=`mktemp -t common.XXXX`
 
-"$CI_ROOT"/script/static-checks/check-copyright.py --tree "$DIRECTORY" $COPYRIGHT_FLAGS --patch --from-ref $(get_merge_base) &> "$LOG_FILE"
+"$CI_ROOT"/script/static-checks/check-copyright.py --tree "$DIRECTORY" $COPYRIGHT_FLAGS --patch --from-ref ${merge_base} &> "$LOG_FILE"
 RES=$?
 
 if [ -s "$LOG_FILE" ]; then