diff --git a/src/tests/servers/app/window_invalidation/Jamfile b/src/tests/servers/app/window_invalidation/Jamfile
index 1a3407422a..27a182b46f 100644
--- a/src/tests/servers/app/window_invalidation/Jamfile
+++ b/src/tests/servers/app/window_invalidation/Jamfile
@@ -3,8 +3,7 @@ SubDir HAIKU_TOP src tests servers app window_invalidation ;
 SetSubDirSupportedPlatformsBeOSCompatible ;
 AddSubDirSupportedPlatforms libbe_test ;
 
-UseHeaders [ FDirName os app ] ;
-UseHeaders [ FDirName os interface ] ;
+UsePrivateHeaders interface ;
 
 Application WindowInvalidation :
 	WindowInvalidation.cpp
diff --git a/src/tests/servers/app/window_invalidation/WindowInvalidation.cpp b/src/tests/servers/app/window_invalidation/WindowInvalidation.cpp
index 9eb5e08299..fda9903b6a 100644
--- a/src/tests/servers/app/window_invalidation/WindowInvalidation.cpp
+++ b/src/tests/servers/app/window_invalidation/WindowInvalidation.cpp
@@ -7,13 +7,14 @@
  */
 
 
+#include <stdlib.h>
+
 #include <Application.h>
 #include <MessageRunner.h>
 #include <Window.h>
 #include <View.h>
 
-//#include <stdio.h>
-#include <stdlib.h>
+#include <WindowPrivate.h>
 
 
 class ShowInvalidationView : public BView {
@@ -108,7 +109,7 @@ void
 ChangingWindow::MessageReceived(BMessage* message)
 {
 	if (message->what == 'actn') {
-		switch (rand() % 3) {
+		switch (rand() % 4) {
 			case 0:
 			{
 				// resize window
@@ -147,6 +148,17 @@ ChangingWindow::MessageReceived(BMessage* message)
 				SetTitle(kChoices[rand() % (sizeof(kChoices) / sizeof(char*))]);
 				break;
 			}
+
+			case 3:
+			{
+				// change look
+				static const window_look kLooks[]
+					= {B_TITLED_WINDOW_LOOK, B_DOCUMENT_WINDOW_LOOK,
+						B_FLOATING_WINDOW_LOOK, kLeftTitledWindowLook};
+
+				SetLook(kLooks[rand() % (sizeof(kLooks) / sizeof(kLooks[0]))]);
+				break;
+			}
 		}
 	} else
 		BWindow::MessageReceived(message);