diff --git src/wp-includes/l10n.php src/wp-includes/l10n.php
index 2317455..6d0feb7 100644
--- src/wp-includes/l10n.php
+++ src/wp-includes/l10n.php
@@ -758,10 +758,18 @@ function get_available_languages( $dir = null ) {
 	$languages = array();
 
 	foreach( (array)glob( ( is_null( $dir) ? WP_LANG_DIR : $dir ) . '/*.mo' ) as $lang_file ) {
-		$lang_file = basename($lang_file, '.mo');
-		if ( 0 !== strpos( $lang_file, 'continents-cities' ) && 0 !== strpos( $lang_file, 'ms-' ) &&
-			0 !== strpos( $lang_file, 'admin-' ))
-			$languages[] = $lang_file;
+		$lang_file   = basename( $lang_file, '.mo' );
+
+		// Get all language files
+		if ( ! is_null( $dir ) && WP_LANG_DIR != $dir ) {
+			$languages[ $lang_file ] = $lang_file;
+
+		// Only keep site language files eg: fr_FR
+		} else {
+			if ( 5 == mb_strlen( $lang_file ) ) {
+				$languages[] = $lang_file;
+			}
+		}
 	}
 
 	return $languages;