Nginx http\u accept无法映射到用于内容协商的变量

目标是获得地图 Content-Type 值转换为文件类型,使用-

# nginx.conf
map $http_accept $suffix {
    "~*turtle" ".ttl";
    default    "DEFAULT";
}

由处理-

# sites-available/site
location /ontologies {
    root /folder;
    add_header Vary Accept;
    add_header X-debug-accept "$http_accept";
    add_header X-debug-suffix "$suffix";
    try_files $uri$suffix $uri =404;
}

然而,回应总是给出-

# curl -I -H "Content-type: text/turtle" URL
http_accept = */*
suffix      = DEFAULT, which is actually (blank)