Credstash configuration on

I’m trying to play with credstash, but with no luck so far. I am running Alternative: install Home Assistant Supervised on a generic Linux host Since docs does not seem to relate to my installation method I tried to make setup on my own. I was able to setup credstash on hassio_supervisor where I can run credstash -t homeassistant get/get and get it working. But when I’m trying to use it I get following error:

Error: Testing configuration at /config
Failed config
  General Errors: 
    - Error loading /config/configuration.yaml: Secret xxx not defined

I’ve read these very few existing topics, but they all mention creating empty secrets.yaml which I did, but that doesn’t help. I suspect I might have installed credstash in wrong place, but I see no other place to do so.