Ambiguous reference bug for namespaces in Flex

Before coming up with a solution for binding read-only accessors a few months ago, I had already tried out various alternatives, among which the following (which was later also pointed out by others through the comments):
[Bindable]
// public getter:
public function get someProperty ():String {
return this._someProperty;
}
// protected setter:
protected function set someProperty (value:String):void {
this._someProperty [...]