Setting vhv.enable to true fails

I can't seem to set vhv.enable=TRUE.  I have another property with the same code that will set (I checked the vmx file) but vhv will not.

System.getModule("foo").setProperty(vm, "vhv.enable", "TRUE");

System.getModule("foo").setProperty(vm, "featMask.vm.hv.capable", "Min:1");

When I check the vmx file, vhv is not set but the featMask is.  Any help would be appreciated.

Orchestrator 5.5.0 - 1281930

ESXi 5.5u1