Code macro fails to render content if language is set to XML

Code macro fails to render content if the language is set to the value 'xml'. An error appears in place of each macro:

Failed to execute the [code] macro. Cause: [String index out of range: 3]. Click on this message for details.

This was first noticed when upgrading an old wiki from version 6 but I have just reproduced the issue on a fresh 8.4.4 installation with absolutely no customisation. It is annoying as it does mean that existing content in our documents matching these conditions no longer displays, so we have to modify each page to set the language to none or plain to work around the problem.

I've attached the full error output text.