Simplesaml configuration

Hi, I'm having a little trouble configuring simplesaml with nginx.

My server config is:

location /simplesaml {
alias /var/simplesamlphp/www;

index index.php;

location ~ \.php(/|$) {
fastcgi_split_path_info ^(.+?\.php)(/.+)$;
fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
fastcgi_param PATH_INFO $fastcgi_path_info;
fastcgi_index index.php;
fastcgi_pass 127.0.0.1:9000;
include fastcgi_params;
}
}

I get the following error:

*203 FastCGI sent in stderr: "Unable to open primary script: /var/simplesamlphp/www/simplesaml/index.php (No such file or directory)"

The problem is that my url is being included in the alias, for example:

/var/simplesamlphp/www/simplesaml/index.php

Should be:

/var/simplesamlphp/www/index.php

Many thanks
Jonny