Building 3.1.0 release fails in stage/part: /var/uhubuild/work/compile/stage/part/KPrPresentationTool.cpp: In constructor ‘KPrPresentationTool::KPrPresentationTool(KPrViewModePresentation&)’: /var/uhubuild/work/compile/stage/part/KPrPresentationTool.cpp:70:63: error: invalid use of incomplete type ‘class QFrame’ m_frame = new QFrame( m_viewMode.canvas()->canvasWidget() ); Adding #include <QFrame> solves the error.