diff --git a/boards/forms/__init__.py b/boards/forms/__init__.py
--- a/boards/forms/__init__.py
+++ b/boards/forms/__init__.py
@@ -490,7 +490,7 @@ class ThreadForm(PostForm):
 
         # Use default tag if no section exists
         if not required_tag_exists:
-            default_tag, created = Tag.objects.get_or_create(
+            default_tag, created = Tag.objects.get_or_create_with_alias(
                     name=default_tag_name, required=True)
             tag_set.add(default_tag)