Canvas2D: crash in QV4

import QtQuick 2.7
import QtQuick.Window 2.2

Window {
    id: window
    width: 360
    height: 360
    visible: true

    Canvas {
        id: canvas
        anchors.fill: parent

        onPaint: {
            var ctx = getContext("2d")
            ctx.clearRect(0, 0, width, height)
            ctx.strokeStyle = "blue"
            ctx.lineWidth = 10
            ctx.beginPath()
            ctx.arc(width / 2, height / 2, width / 2 - ctx.lineWidth / 2, 0, Math.PI * 2) // <==
            ctx.stroke()
        }
    }
}

#0  0x00007ffff71ccc83 in QV4::Value::isString() const (this=0x7fffcb000388)
    at /home/jpnurmi/Projects/qt-59/qtbase/include/QtQml/5.9.0/QtQml/private/../../../../../../qtdeclarative/src/qml/jsruntime/qv4value_p.h:492
#1  0x00007ffff71ccc83 in QV4::Value::stringValue() const (this=0x7fffcb000388)
    at /home/jpnurmi/Projects/qt-59/qtbase/include/QtQml/5.9.0/QtQml/private/../../../../../../qtdeclarative/src/qml/jsruntime/qv4value_p.h:377
#2  0x00007ffff71ccc83 in QV4::Value::toNumberImpl() const (this=0x7fffcb000388) at jsruntime/qv4value.cpp:117
#3  0x00007ffff71c6c3e in QV4::Value::toNumber() const (this=<optimized out>)
    at /home/jpnurmi/Projects/qt-59/qtbase/include/QtQml/5.9.0/QtQml/private/../../../../../../qtdeclarative/src/qml/jsruntime/qv4value_p.h:511
#4  0x00007ffff71c6c3e in QV4::Runtime::method_toDouble(QV4::Value const&) (value=...) at jsruntime/qv4runtime.cpp:1376
#5  0x00007ffff69e7c08 in  ()
#6  0x0000000000c092c0 in  ()
#7  0x0000000000000000 in  ()