lib/kramdown/parser/kramdown/header.rb in kramdown-2.2.1 vs lib/kramdown/parser/kramdown/header.rb in kramdown-2.3.0

@@ -6,10 +6,11 @@
 # This file is part of kramdown which is licensed under the MIT.
 #++
 #
 
 require 'kramdown/parser/kramdown/block_boundary'
+require 'rexml/xmltokens'
 
 module Kramdown
   module Parser
     class Kramdown
 
@@ -38,10 +39,10 @@
       end
       define_parser(:atx_header, ATX_HEADER_START)
 
       protected
 
-      HEADER_ID = /[\t ]{#(?<id>[A-Za-z][\w:-]*)}\z/
+      HEADER_ID = /[\t ]{#(?<id>#{REXML::XMLTokens::NAME_START_CHAR}#{REXML::XMLTokens::NAME_CHAR}*)}\z/
 
       # Returns header text and optional ID.
       def parse_header_contents
         text = @src["contents"]
         text.rstrip!