Qml's SignalSpy does not count emitted signals for property aliases unless they have been connected to first

I have an internal property in an object that I expose to the outside as a readonly property alias. In a test, I would like to confirm that the property change signals are correctly sent out. I listen to the public property alias with a SignalSpy, and I make changes to the internal property. I expect "publicPropertyChanged" signals to be emitted, and that the SignalSpy's count gets incremented.

The publicPropertyChanged signals seem to be emitted, but SignalSpy does not increment its counter. If, however, I additionally listen to the public alias from some other object, then the SignalSpy correctly increments its counter.