diff --git a/composite.cpp b/composite.cpp
index 3895b61c97..d93c8c8ad5 100644
--- a/composite.cpp
+++ b/composite.cpp
@@ -309,6 +309,9 @@ void Toplevel::addDamage( int x, int y, int w, int h )
     if( !compositing())
         return;
     QRect r( x, y, w, h );
+    // resizing the decoration may lag behind a bit and when shrinking there
+    // may be a damage event coming with size larger than the current window size
+    r &= rect();
     damage_region += r;
     r.translate( this->x(), this->y());
     // this could be possibly optimized to damage Workspace only if the toplevel
@@ -319,6 +322,7 @@ void Toplevel::addDamage( int x, int y, int w, int h )
 
 void Toplevel::addDamageFull()
     {
+    damage_region = QRegion(); // first reset e.g. in case of shrinking
     addDamage( rect());
     }
 
diff --git a/events.cpp b/events.cpp
index 446eaae44f..b231958249 100644
--- a/events.cpp
+++ b/events.cpp
@@ -1628,6 +1628,7 @@ bool Unmanaged::windowEvent( XEvent* e )
             if( e->type == Extensions::shapeNotifyEvent() )
                 {
                 detectShape( handle());
+                addDamageFull();
                 if( scene != NULL )
                     scene->windowGeometryShapeChanged( this );
                 }