diff --git a/client.cpp b/client.cpp
--- a/client.cpp
+++ b/client.cpp
@@ -116,7 +116,7 @@
     , m_killHelperPID(0)
     , m_pingTimestamp(XCB_TIME_CURRENT_TIME)
     , m_userTime(XCB_TIME_CURRENT_TIME)   // Not known yet
-    , allowed_actions(nullptr)
+    , allowed_actions()
     , shade_geometry_change(false)
     , sm_stacking_order(-1)
     , activitiesDefined(false)
@@ -1768,7 +1768,7 @@
     if (!isManaged() && !force)
         return;
     NET::Actions old_allowed_actions = NET::Actions(allowed_actions);
-    allowed_actions = nullptr;
+    allowed_actions = NET::Actions();
     if (isMovable())
         allowed_actions |= NET::ActionMove;
     if (isResizable())
diff --git a/effects/desktopgrid/desktopgrid_config.cpp b/effects/desktopgrid/desktopgrid_config.cpp
--- a/effects/desktopgrid/desktopgrid_config.cpp
+++ b/effects/desktopgrid/desktopgrid_config.cpp
@@ -73,7 +73,7 @@
     m_ui->shortcutEditor->addCollection(m_actionCollection);
 
 
-    m_ui->desktopNameAlignmentCombo->addItem(i18nc("Desktop name alignment:", "Disabled"), QVariant(Qt::Alignment(nullptr)));
+    m_ui->desktopNameAlignmentCombo->addItem(i18nc("Desktop name alignment:", "Disabled"), QVariant(Qt::Alignment()));
     m_ui->desktopNameAlignmentCombo->addItem(i18n("Top"), QVariant(Qt::AlignHCenter | Qt::AlignTop));
     m_ui->desktopNameAlignmentCombo->addItem(i18n("Top-Right"), QVariant(Qt::AlignRight | Qt::AlignTop));
     m_ui->desktopNameAlignmentCombo->addItem(i18n("Right"), QVariant(Qt::AlignRight | Qt::AlignVCenter));
diff --git a/effects/trackmouse/trackmouse.cpp b/effects/trackmouse/trackmouse.cpp
--- a/effects/trackmouse/trackmouse.cpp
+++ b/effects/trackmouse/trackmouse.cpp
@@ -83,7 +83,7 @@
 
 void TrackMouseEffect::reconfigure(ReconfigureFlags)
 {
-    m_modifiers = nullptr;
+    m_modifiers = Qt::KeyboardModifiers();
     TrackMouseConfig::self()->read();
     if (TrackMouseConfig::shift())
         m_modifiers |= Qt::ShiftModifier;
diff --git a/events.cpp b/events.cpp
--- a/events.cpp
+++ b/events.cpp
@@ -444,7 +444,7 @@
                 emit opacityChanged(this, old_opacity);
             } else {
                 // forward to the frame if there's possibly another compositing manager running
-                NETWinInfo i(connection(), frameId(), rootWindow(), nullptr, nullptr);
+                NETWinInfo i(connection(), frameId(), rootWindow(), NET::Properties(), NET::Properties2());
                 i.setOpacity(info->opacity());
             }
         }
diff --git a/geometry.cpp b/geometry.cpp
--- a/geometry.cpp
+++ b/geometry.cpp
@@ -894,7 +894,7 @@
 // (the property with the size of the frame remains on the window after the crash).
 void Workspace::fixPositionAfterCrash(xcb_window_t w, const xcb_get_geometry_reply_t *geometry)
 {
-    NETWinInfo i(connection(), w, rootWindow(), NET::WMFrameExtents, nullptr);
+    NETWinInfo i(connection(), w, rootWindow(), NET::WMFrameExtents, NET::Properties2());
     NETStrut frame = i.frameExtents();
 
     if (frame.left != 0 || frame.top != 0) {
diff --git a/group.cpp b/group.cpp
--- a/group.cpp
+++ b/group.cpp
@@ -60,7 +60,7 @@
     if (leader_P != XCB_WINDOW_NONE) {
         leader_client = workspace()->findClient(Predicate::WindowMatch, leader_P);
         leader_info = new NETWinInfo(connection(), leader_P, rootWindow(),
-                                      nullptr, NET::WM2StartupId);
+                                     NET::Properties(), NET::WM2StartupId);
     }
     effect_group = new EffectWindowGroupImpl(this);
     workspace()->addGroup(this);
diff --git a/kcmkwin/kwinrules/ruleswidget.cpp b/kcmkwin/kwinrules/ruleswidget.cpp
--- a/kcmkwin/kwinrules/ruleswidget.cpp
+++ b/kcmkwin/kwinrules/ruleswidget.cpp
@@ -586,7 +586,7 @@
     rules->wmclassmatch = static_cast< Rules::StringMatch >(wmclass_match->currentIndex());
     rules->windowrole = role->text().toUtf8();
     rules->windowrolematch = static_cast< Rules::StringMatch >(role_match->currentIndex());
-    rules->types = nullptr;
+    rules->types = {};
     bool all_types = true;
     for (int i = 0;
             i < types->count();
diff --git a/manage.cpp b/manage.cpp
--- a/manage.cpp
+++ b/manage.cpp
@@ -606,7 +606,7 @@
             if (opacity() == 1.0) {
                 return;
             }
-            NETWinInfo info(connection(), frameId(), rootWindow(), nullptr, nullptr);
+            NETWinInfo info(connection(), frameId(), rootWindow(), NET::Properties(), NET::Properties2());
             info.setOpacity(static_cast<unsigned long>(opacity() * 0xffffffff));
         }
     );
diff --git a/utils.cpp b/utils.cpp
--- a/utils.cpp
+++ b/utils.cpp
@@ -172,7 +172,7 @@
 
 Qt::MouseButtons x11ToQtMouseButtons(int state)
 {
-    Qt::MouseButtons ret = nullptr;
+    Qt::MouseButtons ret = {};
     if (state & XCB_KEY_BUT_MASK_BUTTON_1)
         ret |= Qt::LeftButton;
     if (state & XCB_KEY_BUT_MASK_BUTTON_2)
@@ -188,7 +188,7 @@
 
 Qt::KeyboardModifiers x11ToQtKeyboardModifiers(int state)
 {
-    Qt::KeyboardModifiers ret = nullptr;
+    Qt::KeyboardModifiers ret = {};
     if (state & XCB_KEY_BUT_MASK_SHIFT)
         ret |= Qt::ShiftModifier;
     if (state & XCB_KEY_BUT_MASK_CONTROL)