diff --git a/tests/custom_pk/fields.py b/tests/custom_pk/fields.py
index 2d70c6b6dc..245ede9bc8 100644
--- a/tests/custom_pk/fields.py
+++ b/tests/custom_pk/fields.py
@@ -19,6 +19,9 @@ class MyWrapper:
             return self.value == other.value
         return self.value == other
 
+    def __hash__(self):
+        return hash(self.value)
+
 
 class MyWrapperField(models.CharField):
     def __init__(self, *args, **kwargs):