diff --git a/backup-if-change.sh b/backup-if-change.sh
index 32a6138..e79b3f2 100755
--- a/backup-if-change.sh
+++ b/backup-if-change.sh
@@ -79,6 +79,7 @@ function main()
     if [ -z "$FILE" -o -z "$TARGET_DIR" ]
     then
         echo "option(s) --file or --target-dir is unspecified."
+        show_usage
         exit 1
     fi
     hash_prev=""