I found out that the plugin stops working with the following directives in .htaccess:
RewriteCond %{REQUEST_URI} !\?
RewriteCond %{REQUEST_URI} !\&
RewriteCond %{REQUEST_URI} !\=
RewriteCond %{REQUEST_URI} !\.
RewriteCond %{REQUEST_URI} !\/$
RewriteRule ^(.*[^\/])$ /$1/ [R=301,L]
301 redirects from pages without slash to slash