diff --git a/CONTRIBUTORS.rst b/CONTRIBUTORS.rst
index 0d9e7f9516..c3ec79cc5b 100644
--- a/CONTRIBUTORS.rst
+++ b/CONTRIBUTORS.rst
@@ -254,6 +254,7 @@ Contributors
 * jcronyn
 * Ben Sturmfels
 * Anselm Bradford
+* Mads Jensen
 
 Translators
 ===========
diff --git a/wagtail/tests/search/models.py b/wagtail/tests/search/models.py
index d7d696f798..74d599331e 100644
--- a/wagtail/tests/search/models.py
+++ b/wagtail/tests/search/models.py
@@ -85,7 +85,7 @@ class AnotherSearchTestChild(SearchTest):
 
 
 class SearchTestSubObject(models.Model):
-    parent = models.ForeignKey(SearchTest, related_name='subobjects')
+    parent = models.ForeignKey(SearchTest, related_name='subobjects', on_delete=models.CASCADE)
     name = models.CharField(max_length=255)
 
     def __str__(self):