diff --git a/mod/forum/db/upgrade.php b/mod/forum/db/upgrade.php
index ec874dfa7ee..f68498f8167 100644
--- a/mod/forum/db/upgrade.php
+++ b/mod/forum/db/upgrade.php
@@ -242,6 +242,13 @@ function xmldb_forum_upgrade($oldversion) {
 
     // Moodle v2.9.0 release upgrade line.
     // Put any upgrade step following this.
+    if ($oldversion < 2015102900) {
+        // Groupid = 0 is never valid.
+        $DB->set_field('forum_discussions', 'groupid', -1, array('groupid' => 0));
+
+        // Forum savepoint reached.
+        upgrade_mod_savepoint(true, 2015102900, 'forum');
+    }
 
     return true;
 }
diff --git a/mod/forum/version.php b/mod/forum/version.php
index a6642b11674..a8a7b59c5d4 100644
--- a/mod/forum/version.php
+++ b/mod/forum/version.php
@@ -24,6 +24,6 @@
 
 defined('MOODLE_INTERNAL') || die();
 
-$plugin->version   = 2015051103;       // The current module version (Date: YYYYMMDDXX)
+$plugin->version   = 2015102900;       // The current module version (Date: YYYYMMDDXX)
 $plugin->requires  = 2015050500;       // Requires this Moodle version
 $plugin->component = 'mod_forum';      // Full name of the plugin (used for diagnostics)