s3 Bucket Policy Malformed error

Question

The following bucket policy is returning a malformed error:

{
"Version": "2008-10-17",
"Id":"S3Policy",
"Statement":[
{
"Sid":"1",
"Effect": "Allow",
"Principal": {
"AWS": ["AWSID"]
},
"Action": ["s3:GetObject", "s3:PutObject"],
"Resource": "arn:aws:s3:::BUCKETNAME/*"
]
}
}

I'm trying to create a policy where all files within BUCKETNAME will be readable/writable by the user AWSID -- a 65 character hex ID that I know works.

Any ideas what specifically is returning the error?