RewriteEngine On
RewriteRule ^(.*)/(.*)$ /$1/$2/
RewriteRule ^(.*)/(.*)/$ /?lang=$1&page=$2

ALSO TRIED:

RewriteEngine On
RewriteRule ^(.*)/(.*)$ /?lang=$1&page=$2
RewriteRule ^(.*)/(.*)/$ /?lang=$1&page=$2

(.htaccess located at root)

When using e.g. /en/links everything works.
When using e.g. /en/links/ it breaks. $lang is set to "/" instead of "en", $page to "/links" instead of "links".