Issue with trailing slashes after rewrite

[Nala Gnirut <nala.gnirut@xxxxxxxxx>]

Hi all,
in a shared hosting with no access to httpd.conf, I'm trying to redirect subdomains to different document root using mod_rewrite.

I'm using this rule in a .htaccess file placed in DocumentRoot:

# Change document root for foo.mydomain.com
RewriteCond %{SERVER_NAME} foo.mydomain.com
RewriteCond %{ENV:REDIRECT_STATUS} ^$
RewriteRule .* /foo%{REQUEST_URI} [QSA,L]

This works as expected accessing

foo.mydomain.com
foo.mydomain.com/
foo.mydomain.com/bar/

while

foo.mydomain.com/bar

fails as it's redirected to

/foo/foo/bar instead of /foo/bar

Please note that trailing slashes are automatically added to any rule but the ones rewritten by this rule.

Where's my fault?

Thanks in advance.