--- wp-includes/class-wp-block-parser.php.orig	2018-12-14 15:15:20.000000000 +0100
+++ wp-includes/class-wp-block-parser.php	2018-12-14 14:40:30.000000000 +0100
@@ -374,7 +374,7 @@
 		 * match back in PHP to see which one it was.
 		 */
 		$has_match = preg_match(
-			'/<!--\s+(?<closer>\/)?wp:(?<namespace>[a-z][a-z0-9_-]*\/)?(?<name>[a-z][a-z0-9_-]*)\s+(?<attrs>{(?:(?:[^}]+|}+(?=})|(?!}\s+\/?-->).)*+)?}\s+)?(?<void>\/)?-->/s',
+			'/<!--\s+(?P<closer>\/)?wp:(?P<namespace>[a-z][a-z0-9_-]*\/)?(?P<name>[a-z][a-z0-9_-]*)\s+(?P<attrs>{(?:(?:[^}]+|}+(?=})|(?!}\s+\/?-->).)*+)?}\s+)?(?P<void>\/)?-->/s',
 			$this->document,
 			$matches,
 			PREG_OFFSET_CAPTURE,