diff --git a/mongoengine/document.py b/mongoengine/document.py
index 2de0b1a3..865bb063 100644
--- a/mongoengine/document.py
+++ b/mongoengine/document.py
@@ -854,7 +854,7 @@ class Document(BaseDocument):
         collection = cls._get_collection()
         # 746: when connection is via mongos, the read preference is not necessarily an indication that
         # this code runs on a secondary
-        if not collection.is_mongos and collection.read_preference > 1:
+        if not collection.database.client.is_mongos and collection.read_preference > 1:
             return
 
         # determine if an index which we are creating includes