diff --git a/ksmserver/logout-greeter/main.cpp b/ksmserver/logout-greeter/main.cpp
--- a/ksmserver/logout-greeter/main.cpp
+++ b/ksmserver/logout-greeter/main.cpp
@@ -163,6 +163,9 @@
 
 int main(int argc, char *argv[])
 {
+    // Qt does not currently (5.9.4) support fullscreen on xdg_shell v6.
+    qputenv("QT_WAYLAND_SHELL_INTEGRATION", "wl-shell");
+
     QQuickWindow::setDefaultAlphaBuffer(true);
     QApplication app(argc, argv);
 
diff --git a/ksmserver/shutdowndlg.cpp b/ksmserver/shutdowndlg.cpp
--- a/ksmserver/shutdowndlg.cpp
+++ b/ksmserver/shutdowndlg.cpp
@@ -86,6 +86,7 @@
     // window stuff
     setClearBeforeRendering(true);
     setColor(QColor(Qt::transparent));
+    setFlag(Qt::FramelessWindowHint);
 
     setResizeMode(QQuickView::SizeRootObjectToView);
 
@@ -252,6 +253,7 @@
     // TODO: set a proper window type to indicate to KWin that this is the logout dialog
     // maybe we need a dedicated type for it?
     m_shellSurface->setPosition(geometry().topLeft());
+    m_shellSurface->setSkipTaskbar(true);
 }
 
 void KSMShutdownDlg::slotLogout()
diff --git a/ksmserver/switchuser-greeter/main.cpp b/ksmserver/switchuser-greeter/main.cpp
--- a/ksmserver/switchuser-greeter/main.cpp
+++ b/ksmserver/switchuser-greeter/main.cpp
@@ -135,6 +135,9 @@
 
 int main(int argc, char *argv[])
 {
+    // Qt does not currently (5.9.4) support fullscreen on xdg_shell v6.
+    qputenv("QT_WAYLAND_SHELL_INTEGRATION", "wl-shell");
+
     QQuickWindow::setDefaultAlphaBuffer(true);
     QGuiApplication app(argc, argv);