diff --git a/mod/forum/lib.php b/mod/forum/lib.php
index c0bf984e078..fa122eabc75 100644
--- a/mod/forum/lib.php
+++ b/mod/forum/lib.php
@@ -3819,6 +3819,7 @@ function forum_print_discussion_header(&$post, $forum, $group = -1, $datestring
 
     $post->subject = format_string($post->subject,true);
 
+    $canviewfullnames = has_capability('moodle/site:viewfullnames', $modcontext);
     $timeddiscussion = !empty($CFG->forum_enabletimedposts) && ($post->timestart || $post->timeend);
     $timedoutsidewindow = '';
     if ($timeddiscussion && ($post->timestart > time() || ($post->timeend != 0 && $post->timeend < time()))) {
@@ -3856,7 +3857,7 @@ function forum_print_discussion_header(&$post, $forum, $group = -1, $datestring
     echo '</span>';
     // User name
     echo '<div class="media-body">';
-    $fullname = fullname($postuser, has_capability('moodle/site:viewfullnames', $modcontext));
+    $fullname = fullname($postuser, $canviewfullnames);
     echo '<a href="'.$CFG->wwwroot.'/user/view.php?id='.$post->userid.'&amp;course='.$forum->course.'">'.$fullname.'</a>';
     echo '</div>';
     echo '</div>';
@@ -3924,7 +3925,7 @@ function forum_print_discussion_header(&$post, $forum, $group = -1, $datestring
     // In QA forums we check that the user can view participants.
     if ($forum->type !== 'qanda' || $canviewparticipants) {
         echo '<a href="'.$CFG->wwwroot.'/user/view.php?id='.$post->usermodified.'&amp;course='.$forum->course.'">'.
-             fullname($usermodified).'</a><br />';
+             fullname($usermodified, $canviewfullnames).'</a><br />';
         $parenturl = (empty($post->lastpostid)) ? '' : '&amp;parent='.$post->lastpostid;
     }