QDesktopServices::openUrl() causes access vioaltion

Switched from Qt 4.8.5 32bit to Qt 5.3.2 64bit.

Input: QUrl with QString as parameter.

Scenario:

QString file = QDir::toNativeSeparators("C:/Users/eroeoes/Pictures/rk.png");
QString mailto = "mailto:user@foo.com?subject=Just a test&attachment=\"" + file + "\"";
QDesktopServices::openUrl(QUrl(mailto));

Expected result: Code opens standard mail client.

Given result: Access violation in qdesktopservice.cpp on row 196.