QQmlScriptString and QQmlExpression bug with trivial script

class MyClass : public QObject
{
Q_PROPERTY(QQmlScriptString script READ .. WRITE set_script NOTIFY...)

void set_script (QQmlScriptString script)
{
...
qqml_expression_ = new QQmlExpression(script);

}
private : QQmlExpression *qqml_expression_;
}

MyClass
{
script: 1.0
}

MyClass
{
script: 1.0*1.0
}