calling a function of a parent??

I have a function on the main timeline of a movie:

function somefunction (whichObject) {
some action;
}

My program loads a child swf. In that child swf, I have code to call the function in the parent:

parent.somefunction (someObject);

but AS3 gives me the error:

ReferenceError: Error #1069: Property somefunction not found on flash.display.Stage and there is no default value.
at MethodInfo-7()

It's easy to call functions in children, and I'm sure I've called a parent's function before... what am I missing?

Instead of parent, try owner.