You have to do it before a certain point in Act 1 and rest. Confirmed working. Weird mutual exclusivity though. It would make more sense for Shart and Lae to refuse each other because Shart says so to Wyll.
Yes, I forgot to mention that, you need to rest after it.
Anything before completing the goblin/druid camp slaughter quest worked for me.
I haven't tested if it can be done that way in Act 2 as well, I'll mention it here later if someone not beats me to it.
