Index: SkinTemplate.php
===================================================================
--- SkinTemplate.php	(revision 104876)
+++ SkinTemplate.php	(working copy)
@@ -430,20 +430,25 @@
 		$language_urls = array();
 
 		if ( !$wgHideInterlanguageLinks ) {
+			global $wgDummyLanguageCodes;
 			foreach( $out->getLanguageLinks() as $l ) {
 				$tmp = explode( ':', $l, 2 );
 				$class = 'interwiki-' . $tmp[0];
 				unset( $tmp );
 				$nt = Title::newFromText( $l );
 				if ( $nt ) {
+					$iwLangAttr = $nt->getInterwiki();
+					if( isset( $wgDummyLanguageCodes[$iwLangAttr] ) ) {
+						$iwLangAttr = $wgDummyLanguageCodes[$iwLangAttr];
+					}
 					$language_urls[] = array(
 						'href' => $nt->getFullURL(),
 						'text' => ( $wgContLang->getLanguageName( $nt->getInterwiki() ) != '' ?
 									$wgContLang->getLanguageName( $nt->getInterwiki() ) : $l ),
 						'title' => $nt->getText(),
 						'class' => $class,
-						'lang' => $nt->getInterwiki(),
-						'hreflang' => $nt->getInterwiki(),
+						'lang' => $iwLangAttr,
+						'hreflang' => $iwLangAttr,
 					);
 				}
 			}