diff --git a/app/views/issues/_tags_sidebar.html.erb b/app/views/issues/_tags_sidebar.html.erb
index bb8d2a6..d34e8e8 100644
--- a/app/views/issues/_tags_sidebar.html.erb
+++ b/app/views/issues/_tags_sidebar.html.erb
@@ -1,4 +1,4 @@
-<% unless sidebar_tags.empty? -%>
+<% unless !defined?(sidebar_tags) || sidebar_tags.empty? -%>
   <%= stylesheet_link_tag 'jquery.tagit.css', :plugin => 'redmine_tags' %>
   <%= stylesheet_link_tag 'redmine_tags', :plugin => 'redmine_tags' %>
   <h3><%= l(:tags) %></h3>