diff --git a/includes/parser/Parser.php b/includes/parser/Parser.php
index e803f2db1de..f3df5a90554 100644
--- a/includes/parser/Parser.php
+++ b/includes/parser/Parser.php
@@ -6483,12 +6483,12 @@ class Parser {
 	 * @unstable
 	 */
 	public static function extractBody( string $text ): string {
-		$text = preg_replace( '!^.*?<body[^>]*>!s', '', $text, 1 );
+		$text = preg_replace( '!^(?>.*?<body)[^>]*+>!s', '', $text, 1 );
 		if ( $text === null ) {
-			// T388729: this should never happen
+			// T399064: this should never happen
 			throw new RuntimeException( 'Regex failed: ' . preg_last_error() );
 		}
-		$text = preg_replace( '!</body>\s*</html>\s*$!', '', $text, 1 );
+		$text = preg_replace( '!</body>\s*+</html>\s*+$!', '', $text, 1 );
 		return $text;
 	}