Changing to HFS on a z/OS system doesn't work

Hi, when I conect to a z/OS system SmartFtp is pointing to my userid and lists all PDS. Whe nI try to switch to the HFS with cwd /U I get positioning to first PDS-qualifier U. When I try CWD '/u' I get the message 501 A qualifier in "'.U'" begins with an invalid character. Same message with CWD '/U/'. The slash seems to be not interpretable ! What is wrong ?
Using FTP on Windows I am using the command cd /u to switch to HFS and point to working directory /u

Hello ...

The problem is the hybrid z/OS system. We will look into a fix for it.

Regards,