diff --git a/polymorphic/tests/migrations/0001_initial.py b/polymorphic/tests/migrations/0001_initial.py
index 4707a36..38106a3 100644
--- a/polymorphic/tests/migrations/0001_initial.py
+++ b/polymorphic/tests/migrations/0001_initial.py
@@ -1450,6 +1450,13 @@ class Migration(migrations.Migration):
                 to="tests.ParentModelWithManager",
             ),
         ),
+        migrations.AddField(
+            model_name="childmodelwithmanager",
+            name="field1",
+            field=models.CharField(
+                max_length=10,
+            ),
+        ),
         migrations.AddField(
             model_name="childmodelwithmanager",
             name="polymorphic_ctype",
diff --git a/polymorphic/tests/models.py b/polymorphic/tests/models.py
index 96e361f..494b98f 100644
--- a/polymorphic/tests/models.py
+++ b/polymorphic/tests/models.py
@@ -222,6 +222,7 @@ class ParentModelWithManager(PolymorphicModel):
 
 class ChildModelWithManager(PolymorphicModel):
     # Also test whether foreign keys receive the manager:
+    field1 = models.CharField(max_length=10)  # needed as MyManager uses it
     fk = models.ForeignKey(
         ParentModelWithManager, on_delete=models.CASCADE, related_name="childmodel_set"
     )