diff --git a/cachier/core.py b/cachier/core.py
index 3f6f172..a95dadc 100644
--- a/cachier/core.py
+++ b/cachier/core.py
@@ -194,7 +194,7 @@ class _MongoCore(_BaseCore):
             {
                 '$set': {'being_calculated': False}
             }
-        }
+        )
 
 class _PickleCore(_BaseCore):