diff --git a/mongoengine/queryset/base.py b/mongoengine/queryset/base.py
index 4b8461fe..7efb0fb6 100644
--- a/mongoengine/queryset/base.py
+++ b/mongoengine/queryset/base.py
@@ -1255,7 +1255,7 @@ class BaseQuerySet(object):
 
         result = self._document._get_collection().aggregate(pipeline)
         if IS_PYMONGO_3:
-            result = list(result)
+            result = tuple(result)
         else:
             result = result.get('result')
 
@@ -1285,7 +1285,7 @@ class BaseQuerySet(object):
 
         result = self._document._get_collection().aggregate(pipeline)
         if IS_PYMONGO_3:
-            result = list(result)
+            result = tuple(result)
         else:
             result = result.get('result')
         if result: