diff --git a/composite/compext.c b/composite/compext.c
index 2918556..8dcade2 100644
--- a/composite/compext.c
+++ b/composite/compext.c
@@ -429,6 +429,29 @@ createOverlayWindow (ScreenPtr pScreen)
     return pWin;
 }
 
+int
+updateOverlayWindow(ScreenPtr pScreen)
+{
+	CompScreenPtr cs;
+	WindowPtr pWin; /* overlay window */
+	XID vlist[2];
+
+	cs = GetCompScreen(pScreen);
+	if ((pWin = cs->pOverlayWin) != NULL) {
+		if ((pWin->drawable.width == pScreen->width) &&
+			(pWin->drawable.height == pScreen->height))
+			return Success;
+
+		/* Let's resize the overlay window. */
+		vlist[0] = pScreen->width;
+		vlist[1] = pScreen->height;
+		return ConfigureWindow(pWin, CWWidth | CWHeight, vlist, wClient(pWin));
+	}
+
+	/* Let's be on the safe side and not assume an overlay window is always allocated. */
+	return Success;
+}
+
 static int
 ProcCompositeGetOverlayWindow (ClientPtr client)
 {
diff --git a/composite/compint.h b/composite/compint.h
index 4b0fe08..bc3c618 100644
--- a/composite/compint.h
+++ b/composite/compint.h
@@ -301,4 +301,7 @@ CompositeRealChildHead (WindowPtr pWin);
 int
 DeleteWindowNoInputDevices(pointer value, XID wid);
 
+int
+updateOverlayWindow(ScreenPtr pScreen);
+
 #endif /* _COMPINT_H_ */
diff --git a/hw/xfree86/modes/xf86RandR12.c b/hw/xfree86/modes/xf86RandR12.c
index e2668fb..d6a2cc0 100644
--- a/hw/xfree86/modes/xf86RandR12.c
+++ b/hw/xfree86/modes/xf86RandR12.c
@@ -239,6 +239,9 @@ xf86RandR12SetMode (ScreenPtr	    pScreen,
      */
     xf86SetViewport (pScreen, pScreen->width, pScreen->height);
     xf86SetViewport (pScreen, 0, 0);
+#ifdef COMPOSITE
+    updateOverlayWindow(pScreen);
+#endif /* COMPOSITE */
     if (pRoot)
 	(*scrp->EnableDisableFBAccess) (pScreen->myNum, TRUE);
     return ret;
diff --git a/include/window.h b/include/window.h
index 52b3982..dc574e2 100644
--- a/include/window.h
+++ b/include/window.h
@@ -256,4 +256,8 @@ extern void DisableMapUnmapEvents(
 extern void EnableMapUnmapEvents(
     WindowPtr /* pWin */ );
 
+#ifdef COMPOSITE /* Is this the appropriate place? */
+extern int updateOverlayWindow(ScreenPtr pScreen);
+#endif /* COMPOSITE */
+
 #endif /* WINDOW_H */