diff --git a/mongoengine/document.py b/mongoengine/document.py
index 182733c7..109f8f82 100644
--- a/mongoengine/document.py
+++ b/mongoengine/document.py
@@ -722,7 +722,7 @@ class Document(BaseDocument):
 
         self._changed_fields = list(
             set(self._changed_fields) - set(fields)
-            ) if fields else obj._changed_fields
+        ) if fields else obj._changed_fields
         self._created = False
         return self