diff --git a/modules/filter/filter.module b/modules/filter/filter.module
index 0d3cf62c5f2fe905ccac8bfdb22b690106ce4be3..18f3e39dc77cc01a12b0e6854f7e299eb2d87b9e 100644
--- a/modules/filter/filter.module
+++ b/modules/filter/filter.module
@@ -865,7 +865,7 @@ function _filter_url_trim($text, $length = NULL) {
  */
 function _filter_autop($text) {
   // All block level tags
-  $block = '(?:table|thead|tfoot|caption|colgroup|tbody|tr|td|th|div|dl|dd|dt|ul|ol|li|pre|select|form|blockquote|address|p|h[1-6])';
+  $block = '(?:table|thead|tfoot|caption|colgroup|tbody|tr|td|th|div|dl|dd|dt|ul|ol|li|pre|select|form|blockquote|address|p|h[1-6]|hr)';
 
   // Split at <pre>, <script>, <style> and </pre>, </script>, </style> tags.
   // We don't apply any processing to the contents of these tags to avoid messing