Get SAS working on a probe in KSP 0.90?

In KSP 0.90 (beta), command pods only provide SAS when a pilot is onboard. A probe command pod like the Stayputnik doesn't have a pilot aboard. I tried adding an SAS module to my Stayputnik probes, but this doesn't enable SAS. How does one get SAS working with a probe in KSP 0.90?

There's a similar but obsolete question about SAS on piloted vessels in a much earlier version of KSP. How to get SAS working in Kerbal Space Program

The inline reaction wheels provide rotation torque, but no automatic SAS functionality. This feature now has to be provided by the probe core itself. The Stayputnik as the most basic probe core doesn't have SAS capabilities. The first probe core which provides SAS is the Probodobodyne OKTO.

On a manned ship, you can get SAS capabilities by having a kerbal with the Pilot class on board.