diff --git a/app/views/users/_sidebar.html.erb b/app/views/users/_sidebar.html.erb
index bebd9d8cc..202cdb5a4 100644
--- a/app/views/users/_sidebar.html.erb
+++ b/app/views/users/_sidebar.html.erb
@@ -44,7 +44,7 @@
           </div>
         <% end %>
       <% end %>
-      <% cache "user-profile-sidebar-stats-#{@user.id}-#{@user.last_article_at}-#{@user.last_comment_at}-#{@user.last_followed_at}", expires_in: 10.days do %>
+      <% cache "user-profile-sidebar-stats-#{@user.id}-#{@user.last_article_at&.rfc3339}-#{@user.last_comment_at&.rfc3339}-#{@user.following_tags_count}-#{@user.last_followed_at&.rfc3339}", expires_in: 10.days do %>
         <div class="sidebar-data">
           <div>
             <%= pluralize @user.articles.published.size, "Post" %> Published