diff --git a/mongoengine/queryset/base.py b/mongoengine/queryset/base.py
index 0ad0e03b..81da98d7 100644
--- a/mongoengine/queryset/base.py
+++ b/mongoengine/queryset/base.py
@@ -13,7 +13,6 @@ from bson import json_util
 import pymongo
 import pymongo.errors
 from pymongo.common import validate_read_preference
-from pymongo.collection import ReturnDocument
 
 from mongoengine import signals
 from mongoengine.connection import get_db
@@ -27,6 +26,9 @@ from mongoengine.queryset import transform
 from mongoengine.queryset.field_list import QueryFieldList
 from mongoengine.queryset.visitor import Q, QNode
 
+if IS_PYMONGO_3:
+    from pymongo.collection import ReturnDocument
+
 
 __all__ = ('BaseQuerySet', 'DO_NOTHING', 'NULLIFY', 'CASCADE', 'DENY', 'PULL')