diff --git a/autotests/CMakeLists.txt b/autotests/CMakeLists.txt
index bcc7d1faa0..a7975f7ea9 100644
--- a/autotests/CMakeLists.txt
+++ b/autotests/CMakeLists.txt
@@ -95,6 +95,7 @@ if (XCB_ICCCM_FOUND)
     target_link_libraries( testXcbSizeHints
                            Qt5::Test
                            Qt5::X11Extras
+                           Qt5::Widgets
                            KF5::ConfigCore
                            KF5::WindowSystem
                            XCB::XCB
@@ -242,6 +243,7 @@ target_link_libraries(testScreens
     Qt5::Sensors
     Qt5::Test
     Qt5::X11Extras
+    Qt5::Widgets
     KF5::ConfigCore
     KF5::ConfigGui
     KF5::I18n
@@ -271,8 +273,8 @@ kconfig_add_kcfg_files(testXRandRScreens_SRCS ../settings.kcfgc)
 add_executable( testXRandRScreens ${testXRandRScreens_SRCS} )
 target_link_libraries( testXRandRScreens
                        Qt5::Test
-                       Qt5::Gui
                        Qt5::Sensors
+		       Qt5::Widgets
                        KF5::ConfigCore
                        KF5::ConfigGui
                        KF5::I18n
diff --git a/autotests/tabbox/CMakeLists.txt b/autotests/tabbox/CMakeLists.txt
index e214f89994..a3108e6458 100644
--- a/autotests/tabbox/CMakeLists.txt
+++ b/autotests/tabbox/CMakeLists.txt
@@ -18,7 +18,7 @@ add_executable( testTabBoxClientModel ${testTabBoxClientModel_SRCS} )
 set_target_properties(testTabBoxClientModel PROPERTIES COMPILE_DEFINITIONS "NO_NONE_WINDOW")
 target_link_libraries( testTabBoxClientModel
     Qt5::Core
-    Qt5::Gui
+    Qt5::Widgets
     Qt5::Script
     Qt5::Quick
     Qt5::Test
@@ -50,7 +50,7 @@ add_executable( testTabBoxHandler ${testTabBoxHandler_SRCS} )
 set_target_properties(testTabBoxHandler PROPERTIES COMPILE_DEFINITIONS "NO_NONE_WINDOW")
 target_link_libraries( testTabBoxHandler
     Qt5::Core
-    Qt5::Gui
+    Qt5::Widgets
     Qt5::Script
     Qt5::Quick
     Qt5::Test
diff --git a/effects/coverswitch/coverswitch.cpp b/effects/coverswitch/coverswitch.cpp
index b2c26c41f6..303782c1b1 100644
--- a/effects/coverswitch/coverswitch.cpp
+++ b/effects/coverswitch/coverswitch.cpp
@@ -27,6 +27,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #include <QIcon>
 #include <QMatrix4x4>
 #include <QMouseEvent>
+#include <QFontMetrics>
 #include <KLocalizedString>
 #include <kcolorscheme.h>
 
diff --git a/effects/coverswitch/coverswitch.h b/effects/coverswitch/coverswitch.h
index b058db4d4d..320c0521d3 100644
--- a/effects/coverswitch/coverswitch.h
+++ b/effects/coverswitch/coverswitch.h
@@ -26,6 +26,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #include <QRegion>
 #include <QSize>
 #include <QTimeLine>
+#include <QFont>
 #include <QQueue>
 
 #include <kwineffects.h>
diff --git a/effects/cube/cube.h b/effects/cube/cube.h
index 9745266785..0de8ad53ec 100644
--- a/effects/cube/cube.h
+++ b/effects/cube/cube.h
@@ -27,6 +27,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #include <QQueue>
 #include <QMatrix4x4>
 #include <QTimeLine>
+#include <QFont>
 #include "cube_inside.h"
 #include "cube_proxy.h"
 
diff --git a/effects/flipswitch/flipswitch.h b/effects/flipswitch/flipswitch.h
index 859f30c65f..add05b4ff3 100644
--- a/effects/flipswitch/flipswitch.h
+++ b/effects/flipswitch/flipswitch.h
@@ -25,6 +25,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #include <QMatrix4x4>
 #include <QQueue>
 #include <QTimeLine>
+#include <QFont>
 
 namespace KWin
 {
diff --git a/effects/mouseclick/mouseclick.h b/effects/mouseclick/mouseclick.h
index 40cddeb4c9..afcd170bcd 100644
--- a/effects/mouseclick/mouseclick.h
+++ b/effects/mouseclick/mouseclick.h
@@ -25,6 +25,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #include <kwinglutils.h>
 #include <kwinxrenderutils.h>
 #include <KLocalizedString>
+#include <QFont>
 
 namespace KWin
 {
diff --git a/effects/presentwindows/presentwindows.h b/effects/presentwindows/presentwindows.h
index 4d7f2b1665..6e95bdada9 100644
--- a/effects/presentwindows/presentwindows.h
+++ b/effects/presentwindows/presentwindows.h
@@ -26,6 +26,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 #include <kwineffects.h>
 
+class QMouseEvent;
 class QElapsedTimer;
 class QQuickView;
 
diff --git a/effects/showfps/showfps.cpp b/effects/showfps/showfps.cpp
index f95fb5e9d9..b17aa2342e 100644
--- a/effects/showfps/showfps.cpp
+++ b/effects/showfps/showfps.cpp
@@ -35,6 +35,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #include <math.h>
 #include <QPainter>
 #include <QVector2D>
+#include <QPalette>
 
 namespace KWin
 {
diff --git a/effects/showfps/showfps.h b/effects/showfps/showfps.h
index 3f8909a05e..40c6a86ddd 100644
--- a/effects/showfps/showfps.h
+++ b/effects/showfps/showfps.h
@@ -22,6 +22,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #define KWIN_SHOWFPS_H
 
 #include <QTime>
+#include <QFont>
 
 #include <kwineffects.h>
 
diff --git a/effects/slidingpopups/slidingpopups.cpp b/effects/slidingpopups/slidingpopups.cpp
index 5408c10bfd..548b67457a 100644
--- a/effects/slidingpopups/slidingpopups.cpp
+++ b/effects/slidingpopups/slidingpopups.cpp
@@ -23,6 +23,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 #include <QTimeLine>
 #include <QApplication>
+#include <QFontMetrics>
 
 #include <KWayland/Server/surface_interface.h>
 #include <KWayland/Server/slide_interface.h>
diff --git a/libkwineffects/kwineffects.h b/libkwineffects/kwineffects.h
index cf9fe42cc1..04e77aa1f0 100644
--- a/libkwineffects/kwineffects.h
+++ b/libkwineffects/kwineffects.h
@@ -56,6 +56,7 @@ class QFont;
 class QGraphicsScale;
 class QKeyEvent;
 class QMatrix4x4;
+class QAction;
 
 /**
  * Logging category to be used inside the KWin effects.