diff --git a/rest_framework/tests/test_fields.py b/rest_framework/tests/test_fields.py
index 1b5345ee1..a4d164712 100644
--- a/rest_framework/tests/test_fields.py
+++ b/rest_framework/tests/test_fields.py
@@ -628,16 +628,26 @@ class DecimalFieldTest(TestCase):
         self.assertFalse(DecimalSerializer(data={'decimal_field': '9001.234'}).is_valid())
     
     def test_decimal_is_not_quantized_when_decimal_places_is_none(self):
-        class DecimalSerializer(serializers.Serializer):
-            decimal_field = serializers.DecimalField(required=False)
-        serializer = DecimalSerializer(data={})
+        class LongDecimalFieldModel(models.Model):
+            decimal_field = models.DecimalField(max_digits=20, decimal_places=10, default=0)
+            
+        class DecimalSerializer((serializers.ModelSerializer):
+            class Meta:
+                model = LongDecimalFieldMode
+            decimal_field = serializers.DecimalField(required=False, decimal_places=2)
         
         self.assertTrue(serializer.is_valid())
         self.assertTrue(serializer.data['decimal_field'].as_tuple().exponent, 0)
         
     def test_decimal_is_quantized_when_decimal_places_is_provided(self):
-        class DecimalSerializer(serializers.Serializer):
+        class LongDecimalFieldModel(models.Model):
+            decimal_field = models.DecimalField(max_digits=20, decimal_places=10, default=0)
+            
+        class DecimalSerializer((serializers.ModelSerializer):
+            class Meta:
+                model = LongDecimalFieldMode
             decimal_field = serializers.DecimalField(required=False, decimal_places=2)
+        
         serializer = DecimalSerializer(data={})
         
         self.assertTrue(serializer.is_valid())