diff --git a/src/tests/servers/app/newerClipping/ClientLooper.cpp b/src/tests/servers/app/newerClipping/ClientLooper.cpp
index 94372a18c3..20d8148586 100644
--- a/src/tests/servers/app/newerClipping/ClientLooper.cpp
+++ b/src/tests/servers/app/newerClipping/ClientLooper.cpp
@@ -38,7 +38,7 @@ ClientLooper::MessageReceived(BMessage* message)
 
 			for (int32 i = 0; i < fViewCount; i++) {
 				// the client is slow
-				snooze(20000L);
+//				snooze(40000L);
 				// send the command to redraw a view
 				BMessage command(MSG_DRAWING_COMMAND);
 				command.AddInt32("token", i);
diff --git a/src/tests/servers/app/newerClipping/Desktop.cpp b/src/tests/servers/app/newerClipping/Desktop.cpp
index a27e040f51..b4b25ebf7c 100644
--- a/src/tests/servers/app/newerClipping/Desktop.cpp
+++ b/src/tests/servers/app/newerClipping/Desktop.cpp
@@ -539,6 +539,7 @@ Desktop::MarkDirty(BRegion* region)
 		// add the new dirty region to the culmulative dirty region
 		fDirtyRegion.Include(region);
 
+#if SHOW_GLOBAL_DIRTY_REGION
 if (fDrawingEngine->Lock()) {
 	fDrawingEngine->SetHighColor(255, 0, 0);
 	fDrawingEngine->FillRegion(region);
@@ -546,6 +547,7 @@ if (fDrawingEngine->Lock()) {
 	fDrawingEngine->Unlock();
 	snooze(100000);
 }
+#endif
 
 		// send redraw messages to all windows intersecting the dirty region
 		_TriggerWindowRedrawing(region);
diff --git a/src/tests/servers/app/newerClipping/Desktop.h b/src/tests/servers/app/newerClipping/Desktop.h
index e085f65116..bc2e6f7dd5 100644
--- a/src/tests/servers/app/newerClipping/Desktop.h
+++ b/src/tests/servers/app/newerClipping/Desktop.h
@@ -19,6 +19,8 @@ enum {
 };
 
 #define MULTI_LOCKER 0
+#define SHOW_GLOBAL_DIRTY_REGION 0
+#define SHOW_WINDOW_CONTENT_DIRTY_REGION 0
 
 class Desktop : public BLooper {
  public:
diff --git a/src/tests/servers/app/newerClipping/WindowLayer.cpp b/src/tests/servers/app/newerClipping/WindowLayer.cpp
index 3b6ba5d58e..0b33c10d8f 100644
--- a/src/tests/servers/app/newerClipping/WindowLayer.cpp
+++ b/src/tests/servers/app/newerClipping/WindowLayer.cpp
@@ -322,6 +322,8 @@ WindowLayer::_DrawContents(ViewLayer* layer)
 		dirtyContentRegion.IntersectWith(fDesktop->DirtyRegion());
 
 		if (dirtyContentRegion.CountRects() > 0) {
+
+#if SHOW_WINDOW_CONTENT_DIRTY_REGION
 if (fDrawingEngine->Lock()) {
 	fDrawingEngine->SetHighColor(0, 0, 255);
 	fDrawingEngine->FillRegion(&dirtyContentRegion);
@@ -329,7 +331,7 @@ if (fDrawingEngine->Lock()) {
 	fDrawingEngine->Unlock();
 	snooze(100000);
 }
-
+#endif
 			// send UPDATE message to the client
 			_MarkContentDirty(&dirtyContentRegion);
 
@@ -435,6 +437,14 @@ WindowLayer::_MarkContentDirty(BRegion* contentDirtyRegion)
 		fPendingUpdateSession->Include(contentDirtyRegion);
 	}
 
+	// clip pending update session from current,
+	// current update session, because the backgrounds have been
+	// cleared again already 
+	if (fCurrentUpdateSession) {
+		fCurrentUpdateSession->Exclude(contentDirtyRegion);
+		fEffectiveDrawingRegionValid = false;
+	}
+
 	if (!fUpdateRequested) {
 		// send this to client
 		fClient->PostMessage(MSG_UPDATE);
@@ -456,6 +466,7 @@ WindowLayer::_BeginUpdate()
 			// session enforced
 			fInUpdate = true;
 		}
+		fEffectiveDrawingRegionValid = false;
 	}
 }
 
@@ -468,6 +479,7 @@ WindowLayer::_EndUpdate()
 		fCurrentUpdateSession = NULL;
 	
 		fInUpdate = false;
+		fEffectiveDrawingRegionValid = false;
 	}
 	if (fPendingUpdateSession) {
 		// send this to client
@@ -498,6 +510,13 @@ UpdateSession::Include(BRegion* additionalDirty)
 	fDirtyRegion.Include(additionalDirty);
 }
 
+// Exclude
+void
+UpdateSession::Exclude(BRegion* dirtyInNextSession)
+{
+	fDirtyRegion.Exclude(dirtyInNextSession);
+}
+
 // MoveBy
 void
 UpdateSession::MoveBy(int32 x, int32 y)
diff --git a/src/tests/servers/app/newerClipping/WindowLayer.h b/src/tests/servers/app/newerClipping/WindowLayer.h
index ef169527a3..9a78648c98 100644
--- a/src/tests/servers/app/newerClipping/WindowLayer.h
+++ b/src/tests/servers/app/newerClipping/WindowLayer.h
@@ -27,6 +27,7 @@ class UpdateSession {
 	virtual							~UpdateSession();
 
 			void					Include(BRegion* additionalDirty);
+			void					Exclude(BRegion* dirtyInNextSession);
 
 	inline	BRegion&				DirtyRegion()
 										{ return fDirtyRegion; }