diff --git a/app/helpers/application_helper.rb b/app/helpers/application_helper.rb
index a1d989e25..df976fc74 100644
--- a/app/helpers/application_helper.rb
+++ b/app/helpers/application_helper.rb
@@ -1275,7 +1275,11 @@ module ApplicationHelper
           elsif sep == "@"
             name = remove_double_quotes(identifier)
             u = User.visible.find_by("LOWER(login) = :s AND type = 'User'", :s => name.downcase)
-            link = link_to_user(u, :only_path => only_path, :class => 'user-mention', :mention => true) if u
+            css_classes = ['user-mention']
+            if u && obj && !obj.visible?(u)
+              css_classes += ['no-view-mentioned-user']
+            end
+            link = link_to_user(u, :only_path => only_path, :class => css_classes.join(' '), :mention => true) if u
           end
         end
         (leading + (link || "#{project_prefix}#{prefix}#{repo_prefix}#{sep}#{identifier}#{comment_suffix}"))
diff --git a/public/stylesheets/application.css b/public/stylesheets/application.css
index f8e11b050..405b49011 100644
--- a/public/stylesheets/application.css
+++ b/public/stylesheets/application.css
@@ -159,6 +159,9 @@ a.user.user-mention {
   padding: 0.1em 0.1em;
   border-radius: 0.1em;
 }
+a.user.user-mention.no-view-mentioned-user {
+  background-color: #F3EDD1;
+}
 
 #sidebar a.selected {line-height:1.7em; padding:1px 3px 2px 2px; margin-left:-2px; background-color:#9DB9D5; color:#fff; border-radius:2px;}
 #sidebar a.selected:hover {text-decoration:none;}