--- formatting.php	2013-06-03 11:38:19.823285355 +0300
+++ formatting.new.php	2013-06-03 11:40:39.201270444 +0300
@@ -1862,7 +1862,7 @@
 		}
 
 		// Test for invalid characters
-		if ( !preg_match('/^[a-z0-9-]+$/i', $sub ) ) {
+	  if ( !preg_match('/^[\d|\p{Ll}]+$/u', $sub ) ) {
 			return apply_filters( 'is_email', false, $email, 'sub_invalid_chars' );
 		}
 	}
@@ -3390,4 +3390,4 @@
  */
 function wp_unslash( $value ) {
 	return stripslashes_deep( $value );
-}
\ No newline at end of file
+}