QQuickView fails when load element from assets:/ in Android

I compiled stable branch of Qt with android-g++ configuration, created simple QtQuick 2 project with 2 files main.qml and MyButton.qml

MyButton.qml:
import QtQuick 2.0

Rectangle {
width: 50
height: 50
color: "green"
}

main.qml:
import QtQuick 2.0

Rectangle {
width: 360
height: 360
color: "yellow"
MyButton {}
}

run fails with error message
W/Qt (21559): assets:/qml/q5test01/main.qml:7 (): assets:/qml/q5test01/main.qml:7:5: MyButton is not a type

If i manually copy qml file to /sdcard/q5test01/ and changed for test in qtquick2applicationviewer.cpp

void QtQuick2ApplicationViewer::setMainQmlFile(const QString &file) {
#ifdef Q_OS_ANDROID
setSource(QUrl("/sdcard/q5test01/main.qml"));
#else
...
#endif
}

it works.