diff --git a/wagtail_ab_testing/apps.py b/wagtail_ab_testing/apps.py
index 6699c4d..c96726e 100644
--- a/wagtail_ab_testing/apps.py
+++ b/wagtail_ab_testing/apps.py
@@ -5,3 +5,4 @@ class WagtailAbTestingAppConfig(AppConfig):
     label = "wagtail_ab_testing"
     name = "wagtail_ab_testing"
     verbose_name = "A/B Testing"
+    default_auto_field = "django.db.models.AutoField"