src/Tools/jEdit/src/proofdocument/proof_document.scala

     val matcher =
       Proof_Document.token_pattern.matcher(Token.string_from_tokens(invalid_tokens, start))
 
     while (matcher.find() && invalid_tokens != Nil) {
 			val kind =
-        if (session.syntax().is_command(matcher.group))
+        if (session.current_syntax.is_command(matcher.group))
           Token.Kind.COMMAND_START
         else if (matcher.end - matcher.start > 2 && matcher.group.substring(0, 2) == "(*")
           Token.Kind.COMMENT
         else
           Token.Kind.OTHER