Problem with confirmation URL when using WPML

Hi. I’m trying the plugin on websites with several languages, including portuguese. I’m also using WPML to translate the plugins strings (as the service has a limited language support). Everything seems to be fine except the validation URL that a client receives after subscribing to a list.

The validation URL that misses a forward slash after the language directory:
eg: https://www.domain.com/en?nome=Joao&email=…
It should be https://www.domain.com/en/?nome=Joao&email=…

* this happens if I use the language directory. If I use the language name as a parameter in the URL it results in a token error (it seems the language parameter is interpreted as a subscription parameter)

How can I fix this?
Thank you