.htaccess password protected folder goes to 404 page

Question

I've stumbled upon a strange issue. Lets say I have folder in main domain directory: /myfolder

When I try to access index of files in this folder I go to: myurl.com/myfolder And it works without any problems. Now when I put .htaccess with password protection in this folder like:

AuthUserFile /home/mywebsite/.htpasssomerandomname
AuthType Basic
AuthName "Authentication Required"
Require valid-user

Suddenly instead of asking me for password when I try to access myurl.com/myfolder I get 404 wordpress template page. Below is my .htaccess in main WordPress folder.

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>

Any ideas what might be a problem?

Answer 1

I don't understand why but it seems adding below line to .htaccess inside protected folder fixed this issue:

ErrorDocument 401 "Authorisation Required"

I've found this fix online but without explanation why it actually works that way. Anyone can add explanation? It just feels like it really shouldn't be like that.