diff --git a/mod/forum/view.php b/mod/forum/view.php
index b8c8043442a..4887d1db9dd 100644
--- a/mod/forum/view.php
+++ b/mod/forum/view.php
@@ -219,10 +219,19 @@
             if ($mode) {
                 set_user_preference("forum_displaymode", $mode);
             }
+
+            $groupmode = groups_get_activity_groupmode($cm, $course);
+            $canreply = NULL;
+            if ($groupmode == SEPARATEGROUPS) {
+                if (!has_capability('moodle/site:accessallgroups', $context)) {
+                    $canreply = false;
+                }
+            }
+            
             $displaymode = get_user_preferences("forum_displaymode", $CFG->forum_displaymode);
             $canrate = has_capability('mod/forum:rate', $context);
             echo ' '; // this should fix the floating in FF
-            forum_print_discussion($course, $cm, $forum, $discussion, $post, $displaymode, NULL, $canrate);
+            forum_print_discussion($course, $cm, $forum, $discussion, $post, $displaymode, $canreply, $canrate);
             break;
 
         case 'eachuser':