diff -r 42713dbe6ebe -r e915dd81a279 src/rail_cmd.cpp
--- a/src/rail_cmd.cpp	Tue Mar 13 12:21:13 2007 +0000
+++ b/src/rail_cmd.cpp	Tue Mar 13 13:07:17 2007 +0000
@@ -212,7 +212,7 @@
 				)) { // partly up
 			if (existing != 0) {
 				return 0;
-			} else if (!_patches.build_on_slopes || _is_old_ai_player) {
+			} else if (!_patches.build_on_slopes) {
 				return_cmd_error(STR_1000_LAND_SLOPED_IN_WRONG_DIRECTION);
 			} else {
 				return _price.terraform;
@@ -571,7 +571,6 @@
 	 */
 
 	if (tileh != SLOPE_FLAT && (
-				_is_old_ai_player ||
 				!_patches.build_on_slopes ||
 				IsSteepSlope(tileh) ||
 				!CanBuildDepotByTileh(dir, tileh)