diff --git a/bin/backup-config b/bin/backup-config
index 05020fa..367c65a 100755
--- a/bin/backup-config
+++ b/bin/backup-config
@@ -48,6 +48,9 @@ function __main__() {
         zip -r "$destination" config
     elif [[ "$mode" == "tar" ]]; then
         tar -cf "$destination" config/*
+    else
+        echo "Error: unrecognized mode '$mode'"
+        exit 1
     fi
 }