OSError: [Errno 22] Invalid argument in wait_for_service

[gsnedders]

Traceback (most recent call last):
  File "/Volumes/gsnedders/projects/wpt/web-platform-tests/tools/wptrunner/wptrunner/testrunner.py", line 263, in init
    self.browser.start(group_metadata=group_metadata, **self.browser_settings)
  File "/Volumes/gsnedders/projects/wpt/web-platform-tests/tools/wptrunner/wptrunner/browsers/safari.py", line 297, in start
    super().start(*args, **kwargs)
  File "/Volumes/gsnedders/projects/wpt/web-platform-tests/tools/wptrunner/wptrunner/browsers/base.py", line 339, in start
    self._run_server(group_metadata, **kwargs)
  File "/Volumes/gsnedders/projects/wpt/web-platform-tests/tools/wptrunner/wptrunner/browsers/base.py", line 373, in _run_server
    wait_for_service(
  File "/Volumes/gsnedders/projects/wpt/web-platform-tests/tools/wptrunner/wptrunner/environment.py", line 365, in wait_for_service
    so.connect(addr)
OSError: [Errno 22] Invalid argument

Unclear if something weird is going on, if I have a regression on my branch, or if we're somehow passing None or similar.