Apache配置将https引导至http，然后引导至https

Question

Apache配置

RewriteEngine On
RewriteCond %{HTTP:X-Forwarded-Proto} !https
RewriteRule (.) https://example.com%{REQUEST_URI} [R=301]

Header always merge Vary X-Forwarded-Proto

给出

 
https://example.com/foo/bar --> http://example.com/foo/bar/ --> https://example.com/foo/bar/

我该如何解决？