diff --git a/djongo/models/fields.py b/djongo/models/fields.py
index 327de0267cf41290cd8f44135045d3adde94ec93..6f2033d2e396cb163ba7de69d38673c86ae0f3a4 100644
--- a/djongo/models/fields.py
+++ b/djongo/models/fields.py
@@ -615,6 +615,9 @@ class ObjectIdFieldMixin:
     def rel_db_type(self, connection):
         return self.db_type(connection)
 
+    def get_prep_value(self, value):
+        return value
+
 
 class GenericObjectIdField(ObjectIdFieldMixin, Field):
     pass