--- ../octave.tt/src/graphics.cc	2010-10-26 19:04:14.664016402 +0200
+++ src/graphics.cc	2010-10-29 13:46:13.284014199 +0200
@@ -536,9 +536,14 @@
 static Matrix
 screen_size_pixels (void)
 {
+  Matrix retval = default_screensize();
   graphics_object obj = gh_manager::get_object (0);
-  Matrix sz = obj.get ("screensize").matrix_value ();
-  return convert_position (sz, obj.get ("units").string_value (), "pixels", sz.extract_n (0, 2, 1, 2)).extract_n (0, 2, 1, 2);
+  if (obj.valid_object ())
+    {
+      Matrix sz = obj.get ("screensize").matrix_value ();
+      retval = convert_position (sz, obj.get ("units").string_value (), "pixels", sz.extract_n (0, 2, 1, 2)).extract_n (0, 2, 1, 2);
+    }
+  return retval;
 }
 
 graphics_object