I am trying to update image-type and cluster-version of my cluster with gcloud container clusters upgrade --image-type cos my-cluster --node-pool default-pool --cluster-version=1.7.12-gke.1 but keeps getting this error

CONTAINER_VM cannot be used with Kubernetes 1.7.6 and above. The CONTAINER_VM image is deprecated and no longer supported. Please choose another image type for this upgrade. See: https://cloud.google.com/container-engine/docs/node-images

From kubectl version it says

Client Version: version.Info{Major:"1", Minor:"5", GitVersion:"v1.5.3", GitCommit:"029c3a408176b55c30846f0faedf56aae5992e9b", GitTreeState:"clean", BuildDate:"2017-02-15T06:40:50Z", GoVersion:"go1.7.4", Compiler:"gc", Platform:"linux/amd64"} Server Version: version.Info{Major:"1", Minor:"7+", GitVersion:"v1.7.12-gke.1", GitCommit:"f4f0bedb82a57dc32b21b8f15fe01e0b8411356b", GitTreeState:"clean", BuildDate:"2018-02-05T18:21:59Z", GoVersion:"go1.8.3", Compiler:"gc", Platform:"linux/amd64"}

Why it does not allow me to upgrade while the error telling me clearly to upgrade? Or do I have to downgrade kubernetes server to <= 1.7.6? But how to do so?