diff --git a/mod/forum/lib.php b/mod/forum/lib.php
index 05847e387ef..93f95c35cb6 100644
--- a/mod/forum/lib.php
+++ b/mod/forum/lib.php
@@ -628,7 +628,7 @@ function forum_cron() {
 
                 $shortname = format_string($course->shortname, true, array('context' => get_context_instance(CONTEXT_COURSE, $course->id)));
 
-                $postsubject = "$shortname: ".format_string($post->subject,true);
+                $postsubject = html_to_text("$shortname: ".format_string($post->subject, true));
                 $posttext = forum_make_mail_text($course, $cm, $forum, $discussion, $post, $userfrom, $userto);
                 $posthtml = forum_make_mail_html($course, $cm, $forum, $discussion, $post, $userfrom, $userto);