Index: mod/forum/lib.php
===================================================================
--- mod/forum/lib.php	(revision 16030)
+++ mod/forum/lib.php	(revision )
@@ -4176,7 +4176,8 @@
     $sql = "SELECT f.id
               FROM {$CFG->prefix}forum f
                    LEFT JOIN {$CFG->prefix}forum_subscriptions fs ON (fs.forum = f.id AND fs.userid = $USER->id)
-             WHERE f.forcesubscribe <> ".FORUM_DISALLOWSUBSCRIBE."
+             WHERE f.course = $course->id
+                   AND f.forcesubscribe <> ".FORUM_DISALLOWSUBSCRIBE."
                    AND (f.forcesubscribe = ".FORUM_FORCESUBSCRIBE." OR fs.id IS NOT NULL)";
     if ($subscribed = get_records_sql($sql)) {
         foreach ($subscribed as $s) {