diff --git a/examples/starwars/models.py b/examples/starwars/models.py
index 3964acb..2f80e27 100644
--- a/examples/starwars/models.py
+++ b/examples/starwars/models.py
@@ -5,13 +5,7 @@ from django.db import models
 
 class Character(models.Model):
     name = models.CharField(max_length=50)
-    ship = models.ForeignKey(
-        'Ship',
-        blank=True,
-        null=True,
-        on_delete=models.SET_NULL,
-        related_name='characters'
-    )
+    ship = models.ForeignKey('Ship', blank=True, null=True, related_name='characters')
 
     def __str__(self):
         return self.name
@@ -19,10 +13,7 @@ class Character(models.Model):
 
 class Faction(models.Model):
     name = models.CharField(max_length=50)
-    hero = models.ForeignKey(
-        Character,
-        on_delete=models.SET_NULL,
-    )
+    hero = models.ForeignKey(Character)
 
     def __str__(self):
         return self.name
@@ -30,11 +21,7 @@ class Faction(models.Model):
 
 class Ship(models.Model):
     name = models.CharField(max_length=50)
-    faction = models.ForeignKey(
-        Faction,
-        on_delete=models.SET_NULL,
-        related_name='ships'
-    )
+    faction = models.ForeignKey(Faction, related_name='ships')
 
     def __str__(self):
         return self.name
diff --git a/graphene_django/tests/models.py b/graphene_django/tests/models.py
index 534f1f9..03d19d4 100644
--- a/graphene_django/tests/models.py
+++ b/graphene_django/tests/models.py
@@ -15,11 +15,7 @@ class Pet(models.Model):
 
 class FilmDetails(models.Model):
     location = models.CharField(max_length=30)
-    film = models.OneToOneField(
-        'Film',
-        on_delete=models.CASCADE,
-        related_name='details'
-    )
+    film = models.OneToOneField('Film', related_name='details')
 
 
 class Film(models.Model):
@@ -68,16 +64,8 @@ class CNNReporter(Reporter):
 class Article(models.Model):
     headline = models.CharField(max_length=100)
     pub_date = models.DateField()
-    reporter = models.ForeignKey(
-        Reporter,
-        on_delete=models.SET_NULL,
-        related_name='articles'
-    )
-    editor = models.ForeignKey(
-        Reporter,
-        on_delete=models.SET_NULL,
-        related_name='edited_articles_+'
-    )
+    reporter = models.ForeignKey(Reporter, related_name='articles')
+    editor = models.ForeignKey(Reporter, related_name='edited_articles_+')
     lang = models.CharField(max_length=2, help_text='Language', choices=[
         ('es', 'Spanish'),
         ('en', 'English')