How do I raise objection to main phase in a component's run_phase()

In the run_phase() of a component, I'd like to raise an objection to the main phase so I added the following:

uvm_main_phase::get().raise_objection(this);

and I get this error when it runs:

        UVM_ERROR @ 0 ns: reporter [UVM/PH/NULL_OBJECTION] 'uvm_test_top.foo' attempted to raise an objection on 'main', however 'main' is not a task-based phase node!  (This is a UVM_PHASE_IMP, you have to query the schedule to find the UVM_PHASE_NODE)

Why?  What do I not understand or how should this be done?  

It looks to me like uvm_main_phase is derived from uvm_task_phase so wouldn't that make it a "task-based phase node"?

Thanks.

Walker