Amazon S3 server side encryption

I am attempting to turn on server side encryption when uploading a file asynchronously to Amazon S3. I have the file upload working but cannot figure out where to specify the encryption option. Any ideas?

using (var s3Client = new AmazonS3Client(awsAccessKeyID, awsSecretAccessKey, regionEndPoint))
{
   using (TransferUtility fileTransferUtility = new TransferUtility(s3Client))
   {
     await fileTransferUtility.UploadAsync(filePath, bucketName, objectkey);
   }
}