How to use private remote modules hosted on GitHub on Deno Deploy?

According to Private Modules and Repositories, I can access a private GitHub repo using the

DENO_AUTH_TOKENS

DENO_AUTH_TOKENS

environment variable. How do I achieve this on Deno Deploy? I've tried setting

DENO_AUTH_TOKEN

DENO_AUTH_TOKEN

on my project's settings page but it suggests that DENO_
DENO_
is a reserved prefix.