core-tooltip doesn't work inside core-collapse

[Preston-Landers]

I'm unsure if this is a bug in core-collapse but core-tooltip won't show up inside it.

Example:
https://ele.io/Preston-Landers/tooltip-inside-collapse

Edit: use this link:
http://jsbin.com/hibute/2/edit?html,output

Comment out or delete the core-collapse and then the tooltip will appear around "Tooltip here". Thanks.