diff --git a/django/core/management/commands/flush.py b/django/core/management/commands/flush.py
index f7e769bdac..093c6db7b9 100644
--- a/django/core/management/commands/flush.py
+++ b/django/core/management/commands/flush.py
@@ -72,7 +72,7 @@ The full error: %s""" % (connection.settings_dict['NAME'], e))
                     m for m in models.get_models(app, include_auto_created=True)
                     if router.allow_syncdb(db, m)
                 ])
-            emit_post_sync_signal(all_models, verbosity, interactive, db)
+            emit_post_sync_signal(set(all_models), verbosity, interactive, db)
 
             # Reinstall the initial_data fixture.
             kwargs = options.copy()