Blank screen when viewing GPX file

Hi – I’m after some advice if anyone is able to give it.

I’m in the process of importing a site from Movable Type. The old site has a number of GPX files available for download.

I have set WordPress up to allow GPX files to be uploaded by adding to my functions.php, the following code :

add_filter('upload_mimes', 'custom_upload_mimes');
function custom_upload_mimes ( $existing_mimes=array() ) {

$existing_mimes['gpx'] = array('text/xml');

return $existing_mimes;
}

This is good and allows GPX files to be uploaded.

However on attempted viewing of the GPX file, I just get a blank screen.

If I rename the file to be .txt or .xml, it is displayed as you would expect. However to do this would be a bit of a hack – I’d much rather serve GPX files. Is anyone able to tell me what I’m missing? Unfortunately Google searching this is very difficult!

Many thanks