if ( $namespaces === null || $rebuild ) {
global $wgExtraNamespaces, $wgCanonicalNamespaceNames;
$namespaces = array( NS_MAIN => '' ) + $wgCanonicalNamespaceNames;
+ // Add extension namespaces
+ $namespaces += ExtensionRegistry::getInstance()->getAttribute( 'ExtensionNamespaces' );
if ( is_array( $wgExtraNamespaces ) ) {
$namespaces += $wgExtraNamespaces;
}