diff --git a/mongoengine/base/document.py b/mongoengine/base/document.py
index 719d8866..2ffcbc57 100644
--- a/mongoengine/base/document.py
+++ b/mongoengine/base/document.py
@@ -152,7 +152,8 @@ class BaseDocument(object):
         if isinstance(data["_data"], SON):
             data["_data"] = self.__class__._from_son(data["_data"])._data
         for k in ('_changed_fields', '_initialised', '_created', '_data'):
-            setattr(self, k, data[k])
+            if k in data:
+                setattr(self, k, data[k])
 
     def __iter__(self):
         if 'id' in self._fields and 'id' not in self._fields_ordered: