diff -r 393f77009078 src/newgrf_config.cpp
--- a/src/newgrf_config.cpp	Fri Dec 18 15:56:31 2009 +0000
+++ b/src/newgrf_config.cpp	Fri Dec 18 19:23:22 2009 +0100
@@ -500,5 +500,5 @@
  */
 bool GRFConfig::IsOpenTTDBaseGRF() const
 {
-	return (this->grfid & 0x00FFFFFF) == OPENTTD_GRAPHICS_BASE_GRF_ID;
+	return (this->grfid & 0x000000FF) == (OPENTTD_GRAPHICS_BASE_GRF_ID & 0x000000FF);
 }