diff --git a/hw/xquartz/xpr/xprFrame.c b/hw/xquartz/xpr/xprFrame.c
index 9f5d8a637..42f06efee 100644
--- a/hw/xquartz/xpr/xprFrame.c
+++ b/hw/xquartz/xpr/xprFrame.c
@@ -206,13 +206,16 @@ xprCreateFrame(RootlessWindowPtr pFrame, ScreenPtr pScreen,
 static void
 xprDestroyFrame(RootlessFrameID wid)
 {
+    xp_error err;
     TA_SERVER();
     
     pthread_mutex_lock(&window_hash_mutex);
     x_hash_table_remove(window_hash, wid);
     pthread_mutex_unlock(&window_hash_mutex);
 
-    xp_destroy_window(x_cvt_vptr_to_uint(wid));
+    err = xp_destroy_window(x_cvt_vptr_to_uint(wid));
+    if (err != Success)
+        FatalError("Could not destroy window %i.", (int)x_cvt_vptr_to_uint(wid));
 }
 
 
@@ -366,9 +369,12 @@ xprStartDrawing(RootlessFrameID wid, char **pixelData, int *bytesPerRow)
 static void
 xprStopDrawing(RootlessFrameID wid, Bool flush)
 {
+    xp_error err;
     TA_SERVER();
     
-    xp_unlock_window(x_cvt_vptr_to_uint(wid), flush);
+    err = xp_unlock_window(x_cvt_vptr_to_uint(wid), flush);
+    if(err != Success)
+        FatalError("Could not unlock window %i after drawing.", (int)x_cvt_vptr_to_uint(wid));
 }