Unauthorized configuration value error while migrate app to Ionic Pro

I currently try to migrate our Ionic V1 app to the Ionic Pro service following this guideline: https://ionicframework.com/docs/pro/migration/.

When I execute the command “ionic config set -g backend pro” in my project directory than I always get the error “unauthorized configuration value”. I already updatet to the latest Ionic CLI version and re-executed the command “ionic login” before trying it again. Does someone can help me with this case?

System information:
Cordova CLI: 7.0.1
Ionic Framework Version: 1.3.5
Ionic CLI Version: 2.2.3
Ionic App Lib Version: 2.2.1
ios-deploy version: 1.9.1
ios-sim version: 6.0.0
OS: macOS Sierra
Node Version: v6.9.2
Xcode version: Xcode 9.1 Build version 9B55

This is not the latest Ionic CLI.

thank you - I forgot to restart the terminal after updating the CLI. Now it’s working.