diff --git a/effects.cpp b/effects.cpp
index 3b9fef3b11..c0886442ea 100644
--- a/effects.cpp
+++ b/effects.cpp
@@ -1381,9 +1381,9 @@ double EffectWindowImpl::shadowSaturation( ShadowType type ) const
     return toplevel->workspace()->decorationShadowSaturation( type );
     }
 
-WindowQuadList EffectWindowImpl::buildQuads() const
+WindowQuadList EffectWindowImpl::buildQuads( bool force ) const
     {
-    return sceneWindow()->buildQuads();
+    return sceneWindow()->buildQuads( force );
     }
 
 EffectWindow* effectWindow( Toplevel* w )
diff --git a/effects.h b/effects.h
index 66f4fa3811..f00f87d378 100644
--- a/effects.h
+++ b/effects.h
@@ -243,7 +243,7 @@ class EffectWindowImpl : public EffectWindow
         virtual double shadowBrightness( ShadowType type ) const;
         virtual double shadowSaturation( ShadowType type ) const;
 
-        virtual WindowQuadList buildQuads() const;
+        virtual WindowQuadList buildQuads( bool force = false ) const;
 
         const Toplevel* window() const;
         Toplevel* window();
diff --git a/effects/shadow.cpp b/effects/shadow.cpp
index b239d24b4a..54d5c78111 100644
--- a/effects/shadow.cpp
+++ b/effects/shadow.cpp
@@ -138,6 +138,9 @@ void ShadowEffect::reconfigure( ReconfigureFlags )
     updateShadowColor();
 
     // Load decoration shadow related things
+    bool reconfiguring = false;
+    if( mShadowQuadTypes.count() )
+        reconfiguring = true;
     mShadowQuadTypes.clear(); // Changed decoration? TODO: Unregister?
 #ifdef KWIN_HAVE_OPENGL_COMPOSITING
     if( effects->compositingType() == OpenGLCompositing )
@@ -178,6 +181,12 @@ void ShadowEffect::reconfigure( ReconfigureFlags )
             }
         }
 #endif
+
+    if( reconfiguring )
+        { // Force rebuild of all quads to clear their caches
+        foreach( EffectWindow *w, effects->stackingOrder() )
+            w->buildQuads( true );
+        }
     }
 
 void ShadowEffect::updateShadowColor()
diff --git a/lib/kwineffects.h b/lib/kwineffects.h
index 3c412d69de..d51a30e9ae 100644
--- a/lib/kwineffects.h
+++ b/lib/kwineffects.h
@@ -837,9 +837,10 @@ class KWIN_EXPORT EffectWindow
          * Returns the desired saturation of the shadow.
          */
         virtual double shadowSaturation( ShadowType type ) const = 0;
-
-        // TODO internal?
-        virtual WindowQuadList buildQuads() const = 0;
+        /**
+         * Returns the unmodified window quad list. Can also be used to force rebuilding.
+         */
+        virtual WindowQuadList buildQuads( bool force = false ) const = 0;
     };
 
 class KWIN_EXPORT EffectWindowGroup
diff --git a/scene.cpp b/scene.cpp
index da7247aa39..15becfd306 100644
--- a/scene.cpp
+++ b/scene.cpp
@@ -447,9 +447,9 @@ void Scene::Window::disablePainting( int reason )
     disable_painting |= reason;
     }
 
-WindowQuadList Scene::Window::buildQuads() const
+WindowQuadList Scene::Window::buildQuads( bool force ) const
     {
-    if( cached_quad_list != NULL )
+    if( cached_quad_list != NULL && !force )
         return *cached_quad_list;
     WindowQuadList ret;
     if( toplevel->clientPos() == QPoint( 0, 0 ) && toplevel->clientSize() == toplevel->size())
diff --git a/scene.h b/scene.h
index aeb090b838..680e3433a8 100644
--- a/scene.h
+++ b/scene.h
@@ -182,7 +182,7 @@ class Scene::Window
         void discardShape();
         void updateToplevel( Toplevel* c );
         // creates initial quad list for the window
-        virtual WindowQuadList buildQuads() const;
+        virtual WindowQuadList buildQuads( bool force = false ) const;
         void suspendUnredirect( bool suspend );
     protected:
         WindowQuadList makeQuads( WindowQuadType type, const QRegion& reg ) const;