diff --git a/rest_framework/serializers.py b/rest_framework/serializers.py
index 6320a0751..cf797bdcb 100644
--- a/rest_framework/serializers.py
+++ b/rest_framework/serializers.py
@@ -12,7 +12,7 @@ response content is handled by parsers and renderers.
 """
 from __future__ import unicode_literals
 from django.db import models
-from django.db.models.fields import FieldDoesNotExist
+from django.db.models.fields import FieldDoesNotExist, Field as DjangoField
 from django.utils.translation import ugettext_lazy as _
 from rest_framework.compat import unicode_to_repr
 from rest_framework.utils import model_meta
@@ -939,6 +939,9 @@ class ModelSerializer(Serializer):
             except FieldDoesNotExist:
                 continue
 
+            if not isinstance(model_field, DjangoField):
+                continue
+
             # Include each of the `unique_for_*` field names.
             unique_constraint_names |= set([
                 model_field.unique_for_date,