Schema Violation for config.add headers, expected a string in kong request transformer plugin

After updating from Kong Docker 2.1.4-alpine to 2.2.1-alpine, I noticed some error logs in the console:

W1209 11:47:32.924046       1 queue.go:112] requeuing default/sh.helm.release.v1.myService.v55, err 6 errors occurred:
while processing event: {Update} failed: 400 Bad Request {"message":"schema violation (config.add: {\n  headers = {\n    \"expected a string\"\n  }\n})","name":"schema violation","fields":{"config":{"add":{"headers":["expected a string"]}}},"code":2}
while processing event: {Update} failed: 400 Bad Request {"message":"schema violation (config.add: {\n  headers = {\n    \"expected a string\"\n  }\n})","name":"schema violation","fields":{"config":{"add":{"headers":["expected a string"]}}},"code":2}
while processing event: {Update} failed: 400 Bad Request {"message":"schema violation (config.add: {\n  headers = {\n    \"expected a string\"\n  }\n})","name":"schema violation","fields":{"config":{"add":{"headers":["expected a string"]}}},"code":2}
while processing event: {Update} failed: 400 Bad Request {"message":"schema violation (config.add: {\n  headers = {\n    \"expected a string\"\n  }\n})","name":"schema violation","fields":{"config":{"add":{"headers":["expected a string"]}}},"code":2}
while processing event: {Update} failed: 400 Bad Request {"message":"schema violation (config.add: {\n  headers = {\n    \"expected a string\"\n  }\n})","name":"schema violation","fields":{"config":{"add":{"headers":["expected a string"]}}},"code":2}
while processing event: {Update} failed: 400 Bad Request {"message":"schema violation (config.add: {\n  headers = {\n    \"expected a string\"\n  }\n})","name":"schema violation","fields":{"config":{"add":{"headers":["expected a string"]}}},"code":2}

We are using the request-transformer plugin to do something like this:

apiVersion: configuration.konghq.com/v1
kind: KongPlugin
plugin: request-transformer
metadata:
  name: myService-rq
config:
  add:
    headers:
      - WebApiKey:myWebApiKey

The error log mentions that there is a schema violation and headers are expected to be a string, which does not seem to be the case looking at the official examples here.

config:
  add:
    headers:
    - x-new-header:value
    - x-another-header:something

In some cases this even happens when there is no request transformer and we are not adding any config.add.headers using the plugin.

Has anyone experienced the same problems? Do you have any Idea what I could do to fix this?

Thanks for your support! :wink: