PayPal Express and Member Plugin

Hi WPMU !

How can I change the PayPal button "Subscribe" or Unsubscribe" ?
I would like to translate it in French.
I looked at the gateway.paypalexpress.php file, and change the links of the paypal button :

https://www.paypal.com/en_US/i/btn/btn_subscribe_LG.gif

by

https://www.paypal.com/fr_FR/i/btn/btn_subscribe_LG.gif

But I still have the english button on my website.

Any ideas ?
Thank you :slight_smile: