consolidation::Needed throwing an error

I'm currently looping through all my vm searching for which vm's need consolidation, but the line

> print $vm->runtime->consolidationNeeded;

is throwing this error "Undefined subroutine &VirtualMachineRuntimeInfo::consolidationNeeded".  While something like

> print $vm->runtime->maxCpuUsage;

works fine, so the syntax is correct.  The only thing I can think of is that the boolean type consolidationNeeded was added in vSphere API 5.0, but I don't know why this would be causing the error since everything in out vsphere enviroment is up to date... I think.