diff --git a/effects/fallapart/fallapart.h b/effects/fallapart/fallapart.h
--- a/effects/fallapart/fallapart.h
+++ b/effects/fallapart/fallapart.h
@@ -54,9 +54,10 @@
 public Q_SLOTS:
     void slotWindowClosed(KWin::EffectWindow *c);
     void slotWindowDeleted(KWin::EffectWindow *w);
+    void slotWindowDataChanged(KWin::EffectWindow *w, int role);
 
 private:
-    QHash< const EffectWindow*, double > windows;
+    QHash< EffectWindow*, double > windows;
     bool isRealWindow(EffectWindow* w);
     int blockSize;
 };
diff --git a/effects/fallapart/fallapart.cpp b/effects/fallapart/fallapart.cpp
--- a/effects/fallapart/fallapart.cpp
+++ b/effects/fallapart/fallapart.cpp
@@ -38,6 +38,7 @@
     reconfigure(ReconfigureAll);
     connect(effects, SIGNAL(windowClosed(KWin::EffectWindow*)), this, SLOT(slotWindowClosed(KWin::EffectWindow*)));
     connect(effects, SIGNAL(windowDeleted(KWin::EffectWindow*)), this, SLOT(slotWindowDeleted(KWin::EffectWindow*)));
+    connect(effects, SIGNAL(windowDataChanged(KWin::EffectWindow*,int)), this, SLOT(slotWindowDataChanged(KWin::EffectWindow*,int)));
 }
 
 void FallApartEffect::reconfigure(ReconfigureFlags)
@@ -157,6 +158,7 @@
     const void* e = c->data(WindowClosedGrabRole).value<void*>();
     if (e && e != this)
         return;
+    c->setData(WindowClosedGrabRole, QVariant::fromValue(static_cast<void*>(this)));
     windows[ c ] = 0;
     c->refWindow();
 }
@@ -166,6 +168,25 @@
     windows.remove(c);
 }
 
+void FallApartEffect::slotWindowDataChanged(EffectWindow* w, int role)
+{
+    if (role != WindowClosedGrabRole) {
+        return;
+    }
+
+    if (w->data(role).value<void*>() == this) {
+        return;
+    }
+
+    auto it = windows.find(w);
+    if (it == windows.end()) {
+        return;
+    }
+
+    it.key()->unrefWindow();
+    windows.erase(it);
+}
+
 bool FallApartEffect::isActive() const
 {
     return !windows.isEmpty();