Set specific domain for ALB stickiness cookie

I need to set the domain attribute for the ALB stickiness cookie so that session stickiness behaves the same across two subdomains. For example, for the domains foo.example.com and bar.example.com, I'd want the stickiness cookies to have domain=.example.com. However, I don't see any way to configure that for load-balancer-generated cookies. I also tried using an application cookie that has its domain set in the hope that the ALB would propagate the domain to the AWSALBAPP-* cookies, but that doesn't work either.