diff --git a/app/models/post.rb b/app/models/post.rb
index 7f4fb4254..850fce938 100644
--- a/app/models/post.rb
+++ b/app/models/post.rb
@@ -318,8 +318,8 @@ class Post < ActiveRecord::Base
       increment_tags = tag_array - tag_array_was
       execute_sql("UPDATE tags SET post_count = post_count - 1 WHERE name IN (?)", decrement_tags) if decrement_tags.any?
       execute_sql("UPDATE tags SET post_count = post_count + 1 WHERE name IN (?)", increment_tags) if increment_tags.any?
-      Post.expire_cache_for_all(decrement_tags)
-      Post.expire_cache_for_all(increment_tags)
+      Post.expire_cache_for_all(decrement_tags) if decrement_tags.any?
+      Post.expire_cache_for_all(increment_tags) if increment_tags.any?
       Post.expire_cache_for_all([""]) if new_record? || id <= 100_000
     end
 
diff --git a/app/presenters/post_set_presenters/post.rb b/app/presenters/post_set_presenters/post.rb
index 54a516917..c24c9c7dc 100644
--- a/app/presenters/post_set_presenters/post.rb
+++ b/app/presenters/post_set_presenters/post.rb
@@ -49,8 +49,7 @@ module PostSetPresenters
       if tag
         tag.related_tag_array.map(&:first)
       else
-        tag = Tag.find_or_create_by_name(post_set.tag_string)
-        tag.related_tag_array.map(&:first)
+        []
       end
     end