Value of property Event must be of type String in CloudFormation in TopicConfigurations for an S3 bucket
<p>I have this code in the cloudformation template: </p>

<pre><code>     "MyBucket": {
     "Type" : "AWS::S3::Bucket",
     "Properties" : {
     "NotificationConfiguration": {
              "TopicConfigurations": [
                {
                  "Event": ["s3:ObjectCreated:Put" , "s3:ObjectCreated:Post"], 
                  "Topic": { "Ref": "TopicSNS" }
                }
              ]
            }
}
}
</code></pre>

<p>After testing this code by creating a stack in CloudFormation, I get this error : <code>Value of property Event must be of type String</code> and the creation fails.
What is the raison of that?
Thank you</p>