diff --git a/README.md b/README.md
index d25d2d01..12a662f4 100644
--- a/README.md
+++ b/README.md
@@ -192,7 +192,7 @@ from __future__ import unicode_literals
 from django.db import models
 
 class Message(models.Model):
-    user = models.ForeignKey('auth.User')
+    user = models.ForeignKey('auth.User', on_delete=models.CASCADE)
     message = models.TextField()
     creation_date = models.DateTimeField(auto_now_add=True)
 ```