Multilingual settings applied to

I've a multilingual website where the only content type that does not require translation is the blog.
The blog posts are in English and are not supposed to be translated to other languages.

Therefore I've disabled multilingual support for the "Blog entry" content type. (/admin/content/node-type/blog "Workflow > Multilingual support")

I have the Pathautho module installed and configured to create aliases for blog entries with the following pattern
"users/[user-raw]/blog/...."

Nonetheless URLs of blog posts also include the "en" prefix: "en/users/[user-raw]/blog/..."
And the "en" prefix is hard wired into the interface of the "Automated aliss settings".
See this screenshot.

The language negotiation is "Path prefix with language fallback", but again it should not affect the "blog entry" content type.

How can i get rid of the "en" prefix for the blog posts?

Many thanks in advance,
Marco