diff --git a/lib/gollum/frontend/public/gollum/livepreview/js/pagedown/Markdown.Sanitizer.js b/lib/gollum/frontend/public/gollum/livepreview/js/pagedown/Markdown.Sanitizer.js
index eecd069e..b6709b9c 100644
--- a/lib/gollum/frontend/public/gollum/livepreview/js/pagedown/Markdown.Sanitizer.js
+++ b/lib/gollum/frontend/public/gollum/livepreview/js/pagedown/Markdown.Sanitizer.js
@@ -20,7 +20,7 @@
     }
 
     // (tags that can be opened/closed) | (tags that stand alone)
-    var basic_tag_whitelist = /^(<\/?(b|blockquote|code|del|dd|dl|dt|em|h1|h2|h3|i|kbd|li|ol|p|pre|s|sup|sub|strong|strike|ul)>|<(br|hr)\s?\/?>)$/i;
+    var basic_tag_whitelist = /^(<\/?(b|blockquote|code|del|dd|dl|dt|em|h1|h2|h3|h4|h5|h6|i|kbd|li|ol|p|pre|s|sup|sub|strong|strike|ul)>|<(br|hr)\s?\/?>)$/i;
     // <a href="url..." optional title>|</a>
     // Make https:// ftp:// prefix optional so relative links work. <a href="page1">page one</a>
     var a_white = /^(<a\shref="(((https?|ftp):\/\/|\/))?[-A-Za-z0-9+&@#\/%?=~_|!:,.;\(\)]+"(\stitle="[^"<>]+")?\s?>|<\/a>)$/i;