DFUPLUS spray: Cannot specify no quote character

Given this command line invocation:

dfuplus action=spray server=10.210.40.10 srcip=10.210.40.10 srcfile=/var/lib/HPCCSystems/mydropzone/one_file.txt dstname=one_file dstcluster=mythor format=csv encoding=utf8 maxrecordsize=65536 separator='\t' quote='' overwrite=1 replicate=0 compress=1

This sprays correctly but the Details for the file (shown through ECL Watch) indicates that the default quote character (') has been set. I've tried many versions of setting the quote character in the command line, attempt to nullify it, without success.

This – not establishing a quote character at all – works fine through ECL Watch.