Amazon S3 resets ACL after S3FileInfo OpenWrite stream flush

I'm creating Amazon S3 provider, which provides s3 write stream to external code: My provider will be used following way:

// Some external code (provider usage sample)
using (var outStream = provider.GetStreamToWrite(key)) {
   fsFileStream.CopyTo(outStream);
}

//S3Provider.cs
Stream GetStreamToWrite(string key) 
{
    var a3File = new S3FileInfo(_client,  config.AWSFileBucket, key);
    using (a3File.Create()) { }

    _client.PutACL(new PutACLRequest
        {
            BucketName = _amazonS3StorageConfiguration.AWSFileBucket,
            Key = key,
            CannedACL = S3CannedACL.PublicRead
         });
    return a3File.OpenWrite();
}

File created by this code is unpublished, because ACL was resed by stream flush. How to provide published stream to write? Is there some option to publish file after S3FileStream.Flush()?