Index: src/wp-includes/kses.php
===================================================================
--- src/wp-includes/kses.php	(revision 34729)
+++ src/wp-includes/kses.php	(working copy)
@@ -776,7 +776,7 @@
 	}
 	// Allow HTML comments
 
-	if (!preg_match('%^<\s*(/\s*)?([a-zA-Z0-9]+)([^>]*)>?$%', $string, $matches))
+	if (!preg_match('%^<\s*(/\s*)?([a-zA-Z0-9-]+)([^>]*)>?$%', $string, $matches))
 		return '';
 	// It's seriously malformed