OpenURI not available for DesktopPortal

Hi,

I use awesomewm and have desktop portal running:

ps aux | grep '[x]dg-desktop-portal'

alberto   1880  0.0  0.0 385700  6580 ?        Sl   13:19   0:00 /usr/libexec/xdg-desktop-portal

But this does not expose OpenURI:

alberto@void-live ~ % gdbus introspect --session \                       
  --dest org.freedesktop.portal.Desktop \
  --object-path /org/freedesktop/portal/desktop |
grep -A10 'org.freedesktop.portal.OpenURI'

is empty. I use the gtk portal by default, and use turnstile, with per-user services as directed in the documentation.

Any ideas of can be wrong?

Thanks!