--- a/station_map.h	Wed Apr 12 20:01:52 2006 +0000
+++ b/station_map.h	Wed Apr 12 20:33:01 2006 +0000
@@ -162,6 +162,7 @@
 
 static inline Axis GetRailStationAxis(TileIndex t)
 {
+	assert(IsRailwayStation(t));
 	return HASBIT(GetStationGfx(t), 0) ? AXIS_Y : AXIS_X;
 }