Snapshot AWS error message "Undefined index: Message"

I'm trying to setup an Amazon S3 repository for my backups. When testing the connection, I get the following results:

Connecting to AWS
Using SSL: Yes
Setting Region: US Standard (
Using Storage: Standard
Using ACL: private
Sending file to: Bucket: Directory: Unknown: errno:8 Undefined index: Message /var/www/wp/wp-content/plugins/snapshot/lib/Snapshot/Model/Destination/aws/index.php on line 363

Backups fail to upload to S3. Li'l help?