diff --git a/mongoengine/queryset.py b/mongoengine/queryset.py
index ecd58936..8b627d83 100644
--- a/mongoengine/queryset.py
+++ b/mongoengine/queryset.py
@@ -1032,6 +1032,8 @@ class QuerySet(object):
                          :class:`~bson.code.Code` or string
         :param output: output collection name, if set to 'inline' will try to
                        use :class:`~pymongo.collection.Collection.inline_map_reduce`
+                       This can also be a dictionary containing output options
+                       see: http://docs.mongodb.org/manual/reference/commands/#mapReduce
         :param finalize_f: finalize function, an optional function that
                            performs any post-reduction processing.
         :param scope: values to insert into map/reduce global scope. Optional.