Nginx Problems with 1.4.1 upstream "app"

[shrippen]

Describe the bug
nginx restarting in docker container "simple" with following log message:
nginx: [emerg] host not found in upstream "app" in /etc/nginx/http.d/default.conf:48

Interestingy this doesn't happen in 1.4.0 but I want to change versions because of the bugfix for importing

To Reproduce
Starting the container?
Followed the setup instructions, set up the environment variables.

Expected behavior
Nginx starting and serving the website

LinkAce setup (please complete the following information):

• Version: 1.4.1
• Installed via: Docker
• OS: Unraid