diff --git a/mongoengine/queryset/base.py b/mongoengine/queryset/base.py
index a09cbf99..a648391e 100644
--- a/mongoengine/queryset/base.py
+++ b/mongoengine/queryset/base.py
@@ -1193,9 +1193,7 @@ class BaseQuerySet(object):
         validate_read_preference("read_preference", read_preference)
         queryset = self.clone()
         queryset._read_preference = read_preference
-        queryset._cursor_obj = (
-            None
-        )  # we need to re-create the cursor object whenever we apply read_preference
+        queryset._cursor_obj = None  # we need to re-create the cursor object whenever we apply read_preference
         return queryset
 
     def scalar(self, *fields):