Kubernetes: kubectl patch fails with Error from server: json: cannot unmarshal string into Go value

Is this a BUG REPORT or FEATURE REQUEST?:

/kind bug

What happened:

kubectl --namespace=dev patch serviceaccount default -p '{"imagePullSecrets":[{"name":"gcr-json-key"}]}'

Fails with

Error from server: json: cannot unmarshal string into Go value of type map[string]interface {}

What you expected to happen:

Service account is updated

How to reproduce it (as minimally and precisely as possible):

1. Install minikube
2. choco install kubernetes-cli --version 1.8.5
3. kubectl create namespace dev
4. kubectl --namespace=dev create secret docker-registry gcr-json-key --docker-server=https://eu.gcr.io --docker-username=_json_key --docker-password="---PASSWORD---" [email protected]
5. kubectl --namespace=dev patch serviceaccount default -p '{"imagePullSecrets":[{"name":"gcr-json-key"}]}'

Environment:

• Kubernetes version (use kubectl version):

Client Version: version.Info{Major:"1", Minor:"8", GitVersion:"v1.8.1", GitCommit:"f38e43b221d08850172a9a4ea785a86a3ffa3b3a", GitTreeState:"clean", BuildDate:"2017-10-11T23:27:35Z", GoVersion:"go1.8.3", Compiler:"gc", Platform:"windows/amd64"}
Server Version: version.Info{Major:"1", Minor:"8", GitVersion:"v1.8.0", GitCommit:"0b9efaeb34a2fc51ff8e4d34ad9bc6375459c4a4", GitTreeState:"clean", BuildDate:"2017-11-29T22:43:34Z", GoVersion:"go1.9.1", Compiler:"gc", Platform:"linux/amd64"}

• Cloud provider or hardware configuration:
  minikube

• OS (e.g. from /etc/os-release):
  Windows and minikube