manifest changes are ignored when using hiera_include

I'm experimenting with puppetserver 2 / puppet-agent 1 and I'm running into an issue where changes to manifests don't get picked up by the server.
When I'm making changes to a manifest after starting puppetserver it is working for the first 2 or 3 changes I make.
After that new changes don't get picked up anymore until I restart puppetserver.
I can reproduce that behavior.

For an example session see: https://gist.github.com/roman-mueller/cf776fd180a085a551c2

I'm running:
CentOS 7.0.1406 (but also reproduced it on CentOS 7.1.1503)
puppetserver-2.0.0-1.el7.noarch
puppet-agent-1.0.0-1.el7.x86_64

I've set "environment_timeout = 0" in the "production/environment.conf" - which also should be the default.
Everything else is kept on default settings too.
I've committed my experimental Vagrant environment here:
https://github.com/roman-mueller/puppet4-sandbox
Note that this is using vboxsf but I get the same behavior with local files.

When I'm running strace on the puppetserver PID I can see for the first 2 puppet agent runs that global/manifests/init.pp gets accessed.
After that it is not getting read anymore.
I've also waited 45 minutes, but still the change was not picked up.
Only a restart of the puppetserver fixes it at that point.

WORK AROUND
—
There is no simple work around, but there is a simple patch that can be applied.

The problem is on line 17 of lib/puppet/pops/loaders.rb which says:

@@puppet_system_loader ||= create_puppet_system_loader()

This can be patched to read:

@@puppet_system_loader = create_puppet_system_loader()

QA

risk: medium (manual validate only for now)
probability: medium (hiera_include picking up manifest changes downstream only)
severity: medium (changes not picked up, confusing but possibly not blocking)
test level: acceptance (we should update existing acceptance to ensure an altered manifest is picked up)