diff --git a/deleted.cpp b/deleted.cpp
index f49ff57491..fc557d7430 100644
--- a/deleted.cpp
+++ b/deleted.cpp
@@ -179,7 +179,8 @@ NET::WindowType Deleted::windowType(bool direct, int supportedTypes) const
 
 void Deleted::mainClientClosed(Toplevel *client)
 {
-    m_mainClients.removeAll(static_cast<Client*>(client));
+    if (AbstractClient *c = dynamic_cast<AbstractClient*>(client))
+        m_mainClients.removeAll(c);
 }
 
 xcb_window_t Deleted::frameId() const
diff --git a/input.cpp b/input.cpp
index ea3161f311..361d47c48e 100644
--- a/input.cpp
+++ b/input.cpp
@@ -1130,8 +1130,7 @@ Toplevel *InputRedirection::findToplevel(const QPoint &pos)
             // a deleted window doesn't get mouse events
             continue;
         }
-        if (t->isClient()) {
-            Client *c = static_cast<Client*>(t);
+        if (AbstractClient *c = dynamic_cast<AbstractClient*>(t)) {
             if (!c->isOnCurrentActivity() || !c->isOnCurrentDesktop() || c->isMinimized() || !c->isCurrentTab()) {
                 continue;
             }
diff --git a/layers.cpp b/layers.cpp
index 2aec6181d6..46dd76354f 100644
--- a/layers.cpp
+++ b/layers.cpp
@@ -315,7 +315,10 @@ void Workspace::lowerClient(AbstractClient* c, bool nogroup)
     unconstrained_stacking_order.prepend(c);
     if (!nogroup && c->isTransient()) {
         // lower also all windows in the group, in their reversed stacking order
-        ClientList wins = ensureStackingOrder(static_cast<Client*>(c)->group()->members());
+        ClientList wins;
+        if (Client *client = dynamic_cast<Client*>(c)) {
+            wins = ensureStackingOrder(client->group()->members());
+        }
         for (int i = wins.size() - 1;
                 i >= 0;
                 --i) {
diff --git a/scene.cpp b/scene.cpp
index c46f8d1db6..462eac69bf 100644
--- a/scene.cpp
+++ b/scene.cpp
@@ -275,13 +275,13 @@ void Scene::paintSimpleScreen(int orig_mask, QRegion region)
         // Clip out the decoration for opaque windows; the decoration is drawn in the second pass
         opaqueFullscreen = false; // TODO: do we care about unmanged windows here (maybe input windows?)
         if (w->isOpaque()) {
-            Client *c = NULL;
-            if (topw->isClient()) {
-                c = static_cast<Client*>(topw);
+            AbstractClient *c = dynamic_cast<AbstractClient*>(topw);
+            if (c) {
                 opaqueFullscreen = c->isFullScreen();
             }
+            Client *cc = dynamic_cast<Client*>(c);
             // the window is fully opaque
-            if (c && c->decorationHasAlpha()) {
+            if (cc && cc->decorationHasAlpha()) {
                 // decoration uses alpha channel, so we may not exclude it in clipping
                 data.clip = w->clientShape().translated(w->x(), w->y());
             } else {
@@ -739,8 +739,7 @@ const QRegion &Scene::Window::shape() const
 
 QRegion Scene::Window::clientShape() const
 {
-    if (toplevel->isClient()) {
-        Client *c = static_cast< Client * > (toplevel);
+    if (AbstractClient *c = dynamic_cast< AbstractClient * > (toplevel)) {
         if (c->isShade())
             return QRegion();
     }
@@ -788,14 +787,16 @@ void Scene::Window::resetPaintingEnabled()
     }
     if (!toplevel->isOnCurrentActivity())
         disable_painting |= PAINT_DISABLED_BY_ACTIVITY;
-    if (toplevel->isClient()) {
-        Client *c = static_cast<Client*>(toplevel);
+    if (AbstractClient *c = dynamic_cast<AbstractClient*>(toplevel)) {
         if (c->isMinimized())
             disable_painting |= PAINT_DISABLED_BY_MINIMIZE;
         if (c->tabGroup() && c != c->tabGroup()->current())
             disable_painting |= PAINT_DISABLED_BY_TAB_GROUP;
-        else if (c->isHiddenInternal())
-            disable_painting |= PAINT_DISABLED;
+        if (Client *cc = dynamic_cast<Client*>(c)) {
+            if (cc->isHiddenInternal()) {
+                disable_painting |= PAINT_DISABLED;
+            }
+        }
     }
 }
 
diff --git a/scene_opengl.cpp b/scene_opengl.cpp
index b1ace1cd21..8b3be71d50 100644
--- a/scene_opengl.cpp
+++ b/scene_opengl.cpp
@@ -1386,8 +1386,7 @@ void SceneOpenGL::Window::endRenderWindow()
 
 GLTexture *SceneOpenGL::Window::getDecorationTexture() const
 {
-    if (toplevel->isClient()) {
-        Client *client = static_cast<Client *>(toplevel);
+    if (Client *client = dynamic_cast<Client *>(toplevel)) {
         if (client->noBorder()) {
             return nullptr;
         }