SSTP over IPv6

While setting up SSTP I have a problem getting it to work over IPv6. In the WiKi it is stated that
http://wiki.mikrotik.com/wiki/Manual:IPv6_Overview
MikroTik IPv6 support at the moment:

all PPP (Point-to-point protocols);

What is the meaning of this? That IPv6 is supported as transport protocol, or that IPv6 only is supported inside the tunnel?

Currently I only have it working over IPv4, but would like to provide IPv6 for clients to connect to.