diff --git a/mongoengine/fields.py b/mongoengine/fields.py
index 27434e67..08bbc44c 100644
--- a/mongoengine/fields.py
+++ b/mongoengine/fields.py
@@ -1288,7 +1288,7 @@ class SequenceField(IntField):
             instance._data[self.name] = value
             instance._mark_as_changed(self.name)
 
-        return value
+        return int(value) if value else None
 
     def __set__(self, instance, value):