S3 error (Please use AWS4-HMAC-SHA256)

Like this thread - https://forum.grabaperch.com/forum/08-02-2016-s3-configuration - I am seeing an Amazon S3 error on Runway backups. I'm using a bucket hosted in 'eu-west-2' and with Runway 2.8.34. When DEBUG is switched on, this error shows up in red ...

Array
(
    [type] => 512
    [message] => The authorization mechanism you have provided is not supported. Please use AWS4-HMAC-SHA256.
    [file] => /home/hamsva/public_html/perch/addons/apps/perch_s3/lib/aws/aws-sdk-php/src/Aws/S3/StreamWrapper.php
    [line] => 758
)

I'm only just trying out S3 for Runway backups for the first time, so thought this was my config error. However, a similar setup in Runway 3.0.1 is working perfectly. This leads me to assume that the SHA has changed with Runway moving from version 2 to 3. Perhaps Drew can confirm?

I don't need a fix for this because I suspect that moving this site to Runway 3 will make the problem go away. I'm not ready to move this customer's admin to Perch 3 yet, so we'll stick with the DropBox backups for now. This thread will hopefully serve as a search target in case anyone else using Amazon S3 on Runway 2.8.34 hits the same error.