Properties “Retry attempts” and “Maximum age of record” on an AWS Lambda EventSourceMapping to a DynamoDB Stream

I’m trying to set the properties “Retry attempts” and “Maximum age of record” on an AWS Lambda EventSourceMapping to a DynamoDB Stream - via serverless.yml (serverless.com framework). When the stack is deployed, they keep the default values, and not the values I set. Help? Thanks

My code:

name-of-serverless-function
  handler: src/functions/my.handler
    events:
    - stream:
        type: dynamodb
        batchSize: 1
        maximumRetryAttempts: 2
        maximumRecordAgeInSeconds: 8
        arn: properWorkingARN

I am having this same issue and cannot find a work around. Help!