Rancher Agent v1.2.5 can't be used with no internet

I’m using Rancher v1.6.7 and I can’t get the rancher/agent:v1.2.5 container to run without access to DockerHub. I’m pulling it from a private registry in an air-gapped server, but as soon as the agent container starts it tries to pull (itself) from DockerHub.

I’ve set the registry.default setting in the server to point to my private registry, but that does not seem to help.