What would cause oam to change the url from http to https after authentication?

When I access a protected URL http://<url>, after WNA auth or fallback basic auth succeeds, OAM then redirects to https://<url>. This protocol change is not occurring in our test environment but is in production. Obviously, I have gone through comparing OAM and OHS settings between the two environments and have not found any config differences. This is with OAM 11.1.2.2 and OHS 11.1.1.7. In the particular case I'm focused on right now, the URL being protected is routing through a virtual host from the OHS perspective.