Optimize images with special characters

Hi,

I’ve successfully installed everything required. I can run the optimizer fine on all files in my uploads-folder, except filenames that contain special characters.

One of the files are:

https://site.se/wp-content/uploads/Gr?.jpg "Bad response from optimizer"

Gr? in this case is swedish for grey. I could of course just switch out these with an ‘a’ in the filename, but since this is intended for use with clients I’d rather make it work with any type of filename allowed within WordPress.

I’m running:
Ubuntu 14.04
Wordpress 4.1
littleutils-1.0.32
opt-gif
opt-jpg
opt-png

Anyone who can help on this?

https://www.ads-software.com/plugins/cw-image-optimizer/