diff --git a/mongoengine/queryset/base.py b/mongoengine/queryset/base.py
index d57021fe..c2ad027e 100644
--- a/mongoengine/queryset/base.py
+++ b/mongoengine/queryset/base.py
@@ -302,8 +302,11 @@ class BaseQuerySet(object):
         signals.pre_bulk_insert.send(self._document, documents=docs)
         try:
             ids = self._collection.insert(raw, **write_concern)
+        except pymongo.errors.DuplicateKeyError, err:
+            message = 'Could not save document (%s)';
+            raise NotUniqueError(message % unicode(err))
         except pymongo.errors.OperationFailure, err:
-            message = 'Could not save document (%s)'
+            message = 'Could not save document (%s)';
             if re.match('^E1100[01] duplicate key', unicode(err)):
                 # E11000 - duplicate key error index
                 # E11001 - duplicate key on update