--- forum.orig/post.php	2014-09-08 10:37:21.202171725 +0100
+++ forum/post.php	2014-09-08 10:36:03.473172134 +0100
@@ -122,7 +122,8 @@
         print_error('nopostforum', 'forum');
     }
 
-    if (!$cm->visible and !has_capability('moodle/course:viewhiddenactivities', $coursecontext)) {
+    $modcontext    = context_module::instance($cm->id);
+    if (!$cm->visible and !has_capability('moodle/course:viewhiddenactivities', $modcontext)) {
         print_error("activityiscurrentlyhidden");
     }
 
@@ -206,7 +207,7 @@
         }
     }
 
-    if (!$cm->visible and !has_capability('moodle/course:viewhiddenactivities', $coursecontext)) {
+    if (!$cm->visible and !has_capability('moodle/course:viewhiddenactivities', $modcontext)) {
         print_error("activityiscurrentlyhidden");
     }