Has he/hasn't he?

Hello,

I think I know how to use question tags, but the sentence below is not very clear for me.

Which tag should I use: "has he" or "hasn't he"?

A: "Paul hasn't been drinking for a few months now."

B: "Has he/Hasn't he? I saw him drinking at Bob's party last week."

I would choose "Has he". Am I right?

Thank you