File mask not being applied when g:far#source='ag'

[hbarcelos]

File mask is applied just fine when I'm using rg as source:

:Far src replacement /**/*.js? --source=rg

However, if I switch to ag:

:Far src replacement /**/*.js? --source=ag

Looks like file mask is not being applied, because README.md and package.json will appear in result list.

Am I declaring the file mask wrong?
What would be the proper way?