diff --git a/mod/forum/lib.php b/mod/forum/lib.php
index 2afcabc5470..87630217498 100644
--- a/mod/forum/lib.php
+++ b/mod/forum/lib.php
@@ -8322,8 +8322,14 @@ function forum_get_posts_by_user($user, array $courses, $musthaveaccess = false,
             }
             // Get the forum in question
             $forum = $forums[$forumid];
-            // This is needed for functionality later on in the forum code....
-            $forum->cm = $cm;
+
+            // This is needed for functionality later on in the forum code. It is converted to an object
+            // because the cm_info is readonly from 2.6. This is a dirty hack because some other parts of the
+            // code were expecting an writeable object. See {@link forum_print_post()}.
+            $forum->cm = new stdClass();
+            foreach ($cm as $key => $value) {
+                $forum->cm->$key = $value;
+            }
 
             // Check that either the current user can view the forum, or that the
             // current user has capabilities over the requested user and the requested