Warning: Istio is being downgraded

when one upgrades Istio and sees such a message

You are upgrading Istio and a message like this pops up:

WARNING: Istio is being downgraded from 1.20.0 to 1.19.3.
         Before upgrading, you may wish to use 'istioctl x precheck' to check for upgrade warnings.

Not very obvious what happens the first time one comes across this.

The reason is simple:

  • The control plane is at version 1.20.0.
  • The istioctl binary is at version 1.19.3.

The fix: update istioctl to the matching 1.20.0 version to remove this warning.