SSH communicator with bastion host ignores settings and tries to connect directly

I have been using Packer to build AWS AMIs on a private subnet reached via a bastion host. This works fine up to packer 1.6.1, however, on any version since Packer appears to ignore the bastion host settings altogether and attempts to connect directly to the build instance, which of course, times out as it is not directly reachable.

I have checked the documentation and the change logs, but there does not appear to be any mention of any changes, and my configuration still appears to be in accordance with the docs.

So, my question is:

Has a change been made to how bastion hosts work with the SSH communicator since Packer circa 1.6.1 requiring a different configuration or do I need to file a bug report?