diff --git a/migrations/541-delete-thunderbird-theme-categories.py b/migrations/541-delete-thunderbird-theme-categories.py
index 0738aecd04..7d36b00c0d 100644
--- a/migrations/541-delete-thunderbird-theme-categories.py
+++ b/migrations/541-delete-thunderbird-theme-categories.py
@@ -19,7 +19,7 @@ def run():
                 fx_cat.slug, tb_cat.slug)
             AddonCategory.objects.filter(category=tb_cat).delete()
             # Get rid of `application_id` for Thunderbird category.
-            tb_cat.update(application_id=amo.FIREFOX.id)
+            tb_cat.update(application=amo.FIREFOX.id)
 
     # TODO: Eventually get rid of `application_id` for all Firefox categories.
     #fx_cats.update(application=None)