Prefixing WordPress permalinks with blog and category name

I am really struggling with WordPress permalinks and wondering if what I'm trying to do is not possible.

I would like the following permalink structure:

• domain.com/blog/ <-- blog index
• domain.com/blog/politics/ <-- blog category
• domain.com/blog/politics/who-is-donald-trump <-- blog post

The closest I am able to get is:

• domain.com/blog/ <-- blog index
• domain.com/blog/category/politics/ <-- blog category (note the addition of the word "category")
• domain.com/blog/politics/who-is-donald-trump <-- blog post

For my permalink structure I have it set to: /blog/%category%/%postname%/

And for my category prefix I have it set to: blog

This does actually generate the permalinks in the desired format, however the final posts page doesn't work, and returns a 404 error.

I finally got this working as follows:

Permalink structure set to: /blog/%category%/%postname%/

Category base set to: blog/. (note the period on the end)

This was all fine but in my Yoast post sitemap the URL's contained a period, which was fixed with the following code placed in my theme's functions.php file:

add_filter( 'category_link', function( $term_link, $term_id ) {
    $term_link = home_url('/blog/'. get_term( $term_id )->slug .'/');
    return $term_link; 
}, 10, 2 );