serverless: AWS provider credentials not found

Serverless Framework Version - 1.0.0-rc.2

I have setup accessKeyId and secretAccessKey like this in serverless.yml

provider:
  name: aws
  runtime: nodejs4.3
  stage: prod
  region: us-west-2
  credentials:
      accessKeyId: accessKeyIdhere
      secretAccessKey: secretAccessKeyhere

but when run serverless deploy -v i got following error

Error --------------------------------------------------

     ServerlessError: ServerlessError: AWS provider credentials
     not found. You can find more info on how to set up provider
     credentials in our docs here: https://git.io/viZAC

     For debugging logs, run again after setting SLS_DEBUG env var.

Get Support --------------------------------------------
     Docs:          docs.serverless.com
     Bugs:          github.com/serverless/serverless/issues

     Please report this error. We think it might be a bug.

It should work because this is also one of option i found in document rathan than setup using aws cli