Redirect to https://http://www.mydomain.com

Hello,

I’ve this problem since a long time, I remember to have fixed it editing the code, but of course, after update i lost the edited part.
So I try to search the source of this problem :

I use PIE register since 3 years, but my user, when going in my website (https://www.mydomain.com) are redirect for authentication to https://http://www.mydomain.com

Firefox does not car about that, but safari does and do not allow this redirection.

Do you have an idea of the source of this problem ?
(All my versions of wordpress and pie register are uptodate.

Regards

Alexander Denton