diff --git a/lib/pleroma/web/activity_pub/object_validators/tag_validator.ex b/lib/pleroma/web/activity_pub/object_validators/tag_validator.ex
index 5ce9ab36a..91aeb9dd7 100644
--- a/lib/pleroma/web/activity_pub/object_validators/tag_validator.ex
+++ b/lib/pleroma/web/activity_pub/object_validators/tag_validator.ex
@@ -55,7 +55,7 @@ defmodule Pleroma.Web.ActivityPub.ObjectValidators.TagValidator do
         "#" <> name -> name
         name -> name
       end
-
+      |> String.downcase()
 
     data = Map.put(data, "name", name)