qquickproxytheme failed in Ubuntu 16.04

In file included from /home/qt/work/qt/qtquickcontrols2/src/quickcontrols2/qquickproxytheme.cpp:37:0:
/home/qt/work/qt/qtquickcontrols2/src/quickcontrols2/qquickproxytheme_p.h:83:13: error: ‘TestNamespace::QPixmap TestNamespace::QQuickProxyTheme::fileIconPixmap(const TestNamespace::QFileInfo&, const TestNamespace::QSizeF&, TestNamespace::QPlatformTheme::IconOptions) const’ marked ‘override’, but does not override
QPixmap fileIconPixmap(const QFileInfo &fileInfo, const QSizeF &size,
^
/home/qt/work/qt/qtquickcontrols2/src/quickcontrols2/qquickproxytheme.cpp: In member function ‘TestNamespace::QPixmap TestNamespace::QQuickProxyTheme::fileIconPixmap(const TestNamespace::QFileInfo&, const TestNamespace::QSizeF&, TestNamespace::QPlatformTheme::IconOptions) const’:
/home/qt/work/qt/qtquickcontrols2/src/quickcontrols2/qquickproxytheme.cpp:143:25: error: ‘class TestNamespace::QPlatformTheme’ has no member named ‘fileIconPixmap’
return m_theme->fileIconPixmap(fileInfo, size, iconOptions);
^
/home/qt/work/qt/qtquickcontrols2/src/quickcontrols2/qquickproxytheme.cpp:144:12: error: ‘fileIconPixmap’ is not a member of ‘TestNamespace::QPlatformTheme’
return QPlatformTheme::fileIconPixmap(fileInfo, size, iconOptions);
^
Makefile:2054: recipe for target '.obj/qquickproxytheme.o' failed
make[2]: *** [.obj/qquickproxytheme.o] Error 1