diff --git a/rest_framework/serializers.py b/rest_framework/serializers.py
index caa7c980f..9c53a17af 100644
--- a/rest_framework/serializers.py
+++ b/rest_framework/serializers.py
@@ -456,7 +456,7 @@ class ModelSerializer(Serializer):
 
         kwargs['blank'] = model_field.blank
 
-        if model_field.null:
+        if model_field.null or model_field.blank:
             kwargs['required'] = False
 
         if model_field.has_default():