diff --git src/wp-includes/script-loader.php src/wp-includes/script-loader.php
index d56bbaa06c..d214418b7a 100644
--- src/wp-includes/script-loader.php
+++ src/wp-includes/script-loader.php
@@ -356,7 +356,7 @@ function wp_default_scripts( &$scripts ) {
 	$scripts->add( 'mediaelement-core', "/wp-includes/js/mediaelement/mediaelement-and-player.min.js", array(), '4.2.6-78496d1', 1 );
 	$scripts->add( 'mediaelement-migrate', "/wp-includes/js/mediaelement/mediaelement-migrate$suffix.js", array(), false, 1);
 	did_action( 'init' ) && $scripts->localize( 'mediaelement', 'mejsL10n', array(
-		'language' => get_bloginfo( 'language' ),
+		'language' => get_locale(),
 		'strings'  => array(
 			'mejs.install-flash'       => __( 'You are using a browser that does not have Flash player enabled or installed. Please turn on your Flash player plugin or download the latest version from https://get.adobe.com/flashplayer/' ),
 			'mejs.fullscreen-off'      => __( 'Turn off Fullscreen' ),