Can't use s3 direct upload if bucket prefix is defined

I have S3 Online Storage and Direct Upload configured with the following in nuxeo.conf:

nuxeo.s3storage.bucket=askme
nuxeo.s3storage.awsid=askme
nuxeo.s3storage.awssecret=askme
nuxeo.s3storage.region=us-east-2
nuxeo.s3storage.bucket_prefix=yyyy/
nuxeo.s3storage.cachesize=10GB
nuxeo.s3storage.connection.max=50
nuxeo.s3storage.connection.retry=3
nuxeo.s3storage.connection.timeout=50000
nuxeo.s3storage.socket.timeout=50000
nuxeo.s3storage.useDirectUpload=true
nuxeo.s3storage.transient.bucket=askme
nuxeo.s3storage.transient.awsid=askme
nuxeo.s3storage.transient.awssecret=askme
nuxeo.s3storage.transient.region=us-east-2

Uploads through Web UI fail as shown in screenshot-1. Stack traces are visible in attached server.log.

The direct upload code does not add the prefix to the path when placing a binary in the transient store (i.e. binaries appear in the root level of the transient bucket)

When nuxeo.s3storage.bucket_prefix is commented out, everything works as expected.

This has been observed on 9.10 (amazon-s3-direct-upload-1.0.0) and 10.2 (amazon-s3-direct-upload-1.1.1)