Env vars and default values in scaling configuration

Configuration
1

I’m trying to achieve the following:

environment:
  - SCALE_RANGE=2-4
services:
  foo:
    ...
    environment:
      - "*"
    scale:
      count: ${SCALE_RANGE}
      ...

i.e. a self-contained sane default in convox.yml that can be overridden if necessary. (The above fails with a Template format error: Unresolved resource dependencies [AutoscalingTarget].)

How come the default value doesn’t work in this case?