diff --git src/wp-admin/options.php src/wp-admin/options.php
index 93c69bc..a20c11d 100644
--- src/wp-admin/options.php
+++ src/wp-admin/options.php
@@ -218,14 +218,12 @@ if ( 'update' == $action ) {
 		}
 
 		// Switch translation in case WPLANG was changed.
-		$language      = get_option( 'WPLANG' );
-		$user_language = get_user_locale();
+		$language          = get_option( 'WPLANG' );
+		$GLOBALS['locale'] = $language ? $language : 'en_US';
+		$user_language     = get_user_locale();
+
 		if ( $language === $user_language ) {
-			if ( $language ) {
-				load_default_textdomain( $language );
-			} else {
-				unload_textdomain( 'default' );
-			}
+			load_default_textdomain( $language );
 		}
 	}