"billing address is the same as above" doesn't show/hide billing address fields

To replicate on the demo server:

• Add a profile to a contribution page that has all the required fields to expose the "billing address is the same as above" checkbox ("Name and Address" works).
• Load the page.
• Click the checkbox.

Expected behavior:

• Checking/unchecking the box should show/hide the billing fields.

Actual behavior:

• No change.

It's not a JS error because JS is still firing.