diff --git a/rest_framework/serializers.py b/rest_framework/serializers.py
index d8ea02ba3..29b6aaf37 100644
--- a/rest_framework/serializers.py
+++ b/rest_framework/serializers.py
@@ -904,7 +904,7 @@ class ModelSerializer(Serializer):
 
         if getattr(obj, '_m2m_data', None):
             for accessor_name, object_list in obj._m2m_data.items():
-                field = obj._meta.get_field_by_name(accessor_name)[0]
+                field = self.fields[accessor_name]
                 field.save_serializer_data(obj, accessor_name, object_list)
             del(obj._m2m_data)