Index: wp-includes/formatting.php
===================================================================
--- wp-includes/formatting.php	(revision 21629)
+++ wp-includes/formatting.php	(working copy)
@@ -2827,7 +2827,7 @@
 
 		case 'WPLANG':
 			$allowed = get_available_languages();
-			if ( ! in_array( $value, $allowed ) && ! empty( $value ) )
+			if ( in_array( $value, $allowed ) && ! empty( $value ) )
 				$value = get_option( $option );
 			break;