nginx server-side scripting doesn't work as intended with subrequest

[ahmubashshir]

GET /requested/path/ with nginx server-side scripting

<title>Files <!--# echo var="document_uri" default="" --></title>

would generate.

<title>Files /requested/path/</title>

but it generates

<title>Files /static/header.html</title>

after configuring fancyindex header with subrequest.
it'd be great if we could access original request properties as something like $fancyindex_var_<orig-var> or $http_x_fancyindex_<var>