htaccess redirection problem alias vs. directory name

Question

When I use this rule:

RewriteRule ^Chats/([^/]+)/?$ Chats/ChatPage.php?chaturl=$1 [NC] I get $_GET["chaturl"] as ChatPage.php where I should get $1. How can I solve it?

If alias and directory name are not the same, there is no problem. If I use RewriteRule ^Chat/([^/]+)/?$ Chats/ChatPage.php?chaturl=$1 [NC] (NOTICE IT'S CHAT NOW NOT CHATS) There is not problem. $_GET["chaturl"] returns $1 as it should be.

I am asking for best practive: What should I do to get the first one work?