diff --git a/boards/management/commands/cleantags.py b/boards/management/commands/cleantags.py
--- a/boards/management/commands/cleantags.py
+++ b/boards/management/commands/cleantags.py
@@ -13,7 +13,7 @@ class Command(BaseCommand):
 
     @transaction.atomic
     def handle(self, *args, **options):
-        empty = Tag.objects.annotate(num_threads=Count('thread'))\
+        empty = Tag.objects.annotate(num_threads=Count('thread_tags'))\
                 .filter(num_threads=0).order_by('-required', 'name')
         print('Removing {} empty tags'.format(empty.count()))
         empty.delete()