diff --git a/src/rail_gui.cpp b/src/rail_gui.cpp
--- a/src/rail_gui.cpp
+++ b/src/rail_gui.cpp
@@ -818,7 +818,7 @@ static void StationBuildWndProc(Window *
 				SetTileSelectSize(x, y);
 		}
 
-		int rad = (_patches.modified_catchment) ? CA_TRAIN : 4;
+		int rad = (_patches.modified_catchment) ? CA_TRAIN : CA_UNMODIFIED;
 
 		if (_station_show_coverage)
 			SetTileSelectBigSize(-rad, -rad, 2 * rad, 2 * rad);