serverless framework/cli configuration file

serverless.yaml

service: "sadiavasio"
provider: "aws"
functions:
  sadiavas:
    handler: "index.graphql"
    include:
      - blog/
    events: 
      - http:
          path: "blog/graphql"
          method: "POST"

    custom: 
      excludePatterns: []
      optimize: 
        exclude: 
          - "aws-sdk"
        transforms: 
          - 
            name: "babelify"
            opts: 
              presets: 
                - "es2015"

defaults:
  stage: "dev"
  region: "us-west-2"
  memory: 1024
  timeout: 6

resources:
  Resources: 
    PostsDynamo: 
      Type: "AWS::DynamoDB::Table"
      DeletionPolicy: "Retain"
      Properties: 
        AttributeDefinitions: 
          - 
            AttributeName: "id"
            AttributeType: "S"
        KeySchema: 
          - 
            AttributeName: "id"
            KeyType: "HASH"
        ProvisionedThroughput: 
          ReadCapacityUnits: 1
          WriteCapacityUnits: 1
        TableName: "${service}-posts-${stage}"
    AuthorsDynamo: 
      Type: "AWS::DynamoDB::Table"
      DeletionPolicy: "Retain"
      Properties: 
        AttributeDefinitions: 
          - 
            AttributeName: "id"
            AttributeType: "S"
        KeySchema: 
          - 
            AttributeName: "id"
            KeyType: "HASH"
        ProvisionedThroughput: 
          ReadCapacityUnits: 1
          WriteCapacityUnits: 1
        TableName: "${service}-authors-${stage}"
    CommentsDynamo: 
      Type: "AWS::DynamoDB::Table"
      DeletionPolicy: "Retain"
      Properties: 
        AttributeDefinitions: 
          - 
            AttributeName: "id"
            AttributeType: "S"
        KeySchema: 
          - 
            AttributeName: "id"
            KeyType: "HASH"
        ProvisionedThroughput: 
          ReadCapacityUnits: 1
          WriteCapacityUnits: 1
        TableName: "${service}-comments-${stage}"

I get the following error when using this template:

Invalid variable reference syntax for variable stage.
     You can only reference env vars, options, & files. You
     can check our docs for more info.

I believe its related to the line TableName: "${service}-comments-${stage}"

I think it should be ${self:service}-comments-${opt:stage} with the 1.0.0-rc.1 release