diff --git a/django/db/migrations/executor.py b/django/db/migrations/executor.py
index eb738cf4571f..13afa5988f68 100644
--- a/django/db/migrations/executor.py
+++ b/django/db/migrations/executor.py
@@ -224,6 +224,9 @@ def _migrate_all_backwards(self, plan, full_plan, fake):
         # remaining applied migrations.
         last_unapplied_migration = plan[-1][0]
         state = states[last_unapplied_migration]
+        # Avoid mutating state with apps rendered as it's an expensive
+        # operation.
+        del state.apps
         for index, (migration, _) in enumerate(full_plan):
             if migration == last_unapplied_migration:
                 for migration, _ in full_plan[index:]: