If you try to download a file with non ASCII characters – wontÆØÅwork.svg – you will get a 500 Internal Server Error.

By checking the logs, you will find this:

request.CRITICAL:
Uncaught PHP Exception InvalidArgumentException: "The filename fallback must only contain ASCII characters." at /var/www/ez-001/2016/app/bootstrap.php.cache line 1998

{"exception":"[object] (
InvalidArgumentException(code: 0):
The filename fallback must only contain ASCII characters.
at /var/www/ez-001/2016/app/bootstrap.php.cache:1998
)"}

The error seems to come from the ResponseHeaderBag.php file:

 * @param string $filenameFallback A string containing only ASCII characters that
 *     is semantically equivalent to $filename. If the filename is already ASCII,
 *     it can be omitted, or just copied from $filename
public function makeDisposition($disposition, $filename, $filenameFallback = '') 
{   
...
	// filenameFallback is not ASCII.
	if (!preg_match('/^[\x20-\x7e]*$/', $filenameFallback)) {
		throw new \InvalidArgumentException('The filename fallback must only contain ASCII characters.');
	}

I'm not sure why the name wasn't normalized.

Steps to reproduce.

1. Choose any file and rename it to wontÆØÅwork.ext
2. Open the admin interface, create a new file and upload wontÆØÅwork.ext
3. Open that content object with the wontÆØÅwork.ext in the frontend, and try to download it.