diff --git a/mod/forum/classes/local/vaults/discussion_list.php b/mod/forum/classes/local/vaults/discussion_list.php
index 41866143d3c..e099a671ae0 100644
--- a/mod/forum/classes/local/vaults/discussion_list.php
+++ b/mod/forum/classes/local/vaults/discussion_list.php
@@ -350,7 +350,7 @@ class discussion_list extends db_table_vault {
             $favouritesort .= ", {$favalias}.itemtype DESC";
         }
 
-        return "{$alias}.pinned DESC $favouritesort , {$keyfield} {$direction}";
+        return "{$alias}.pinned DESC $favouritesort , {$keyfield} {$direction}, {$alias}.id {$direction}";
     }
 
     /**
diff --git a/mod/forum/tests/behat/discussion_navigation.feature b/mod/forum/tests/behat/discussion_navigation.feature
index 4caa84a7081..045547a63d0 100644
--- a/mod/forum/tests/behat/discussion_navigation.feature
+++ b/mod/forum/tests/behat/discussion_navigation.feature
@@ -51,6 +51,11 @@ Feature: A user can navigate to previous and next discussions
     And I follow "Reply"
     And I set the following fields to these values:
       | Message | Answer to discussion |
+    # We need to wait a bit to guarantee that the post is created after the previous ones.
+    # because there is a bug in the forum_get_discussion_neighbours() when all the discussion
+    # last modified times are the same. See MDL-79247 for more details. Once that bug is fixed
+    # we can remove this wait.
+    And I wait "1" seconds
     And I press "Post to forum"
     And I should not see "Discussion 2"
     And I should see "Discussion 3"