QML Introspection of QDeclarativeItem derived classes fails in QtCreator

Given the following classes:
class A : public QDeclarativeItem

;
in a simple qmake project, the QML text editor and the QML designer do not show the QML Item properties for instances of B. This fragment:
B

gives the error:
'anchors' is not a valid property name.
Activating autocompletion in the instance of B does not show any of the properties defined in A or QDeclarativeItem. The QDeclarativeItem properties are visible in instances of A.