UTF-8 calendar names not displayed correctly

I have a calendar with a greek title, and both in khal printcalendars and in the event editor in ikhal I see a blank space instead of the name. Greek event titles appear correctly.

In the debug logs, I see

Found no or empty file `displayname`

for the greek calendar. And in the config print I get:

debug: Using config:                                                              
debug: [calendars]                                                     
debug:   [[]]
debug: ....

I have metadata = ["displayname", "color"] in vdirsyncer config but the displayname file doesn't get created.
Creating a displayname file in the calendar's vdir shows the calendar name. But I have other calendars in ascii with no displayname files and khal deduces their name from the path correctly (I think).

Reproduce the issue with a calendar whose name contains Greek characters, checking both khal printcalendars and the event editor in ikhal. Compare the debug output and vdir contents with an ASCII-named calendar, then verify that the Greek calendar name is displayed without requiring a manually created displayname file.