quick vac line question - where does this one go ? Pic

I got this purple vac line coming out of the firewall on my 89 XJ, and I cant find where it goes. I did yank the axle vac disco setup years ago.. I cant remember if I need to plug this line up or if it goes somewhere ? The jeep has been sitting for a while and I was going over it and found it laying there sucking in air.

Its a 89 XJ with a 4.0/auto

Any help, Thanks !

Looks like that's the vac line for the heater control valve.

Yep, that's the one.

Ah.. Very good ! Yep, I remember now.. I eliminated that leaking thing a while back. Thanks. So I'll plug this line up.