diff -r 6d64230b9fb9 -r 51bff16a04c9 src/landscape.cpp
--- a/src/landscape.cpp	Thu Dec 18 18:47:39 2008 +0000
+++ b/src/landscape.cpp	Fri Dec 19 01:32:07 2008 +0200
@@ -654,7 +654,7 @@
 
 
 TileIndex _cur_tileloop_tile;
-#define TILELOOP_BITS 4
+#define TILELOOP_BITS 1
 #define TILELOOP_SIZE (1 << TILELOOP_BITS)
 #define TILELOOP_ASSERTMASK ((TILELOOP_SIZE - 1) + ((TILELOOP_SIZE - 1) << MapLogX()))
 #define TILELOOP_CHKMASK (((1 << (MapLogX() - TILELOOP_BITS))-1) << TILELOOP_BITS)
@@ -665,6 +665,7 @@
 
 	assert((tile & ~TILELOOP_ASSERTMASK) == 0);
 	uint count = (MapSizeX() / TILELOOP_SIZE) * (MapSizeY() / TILELOOP_SIZE);
+
 	do {
 		_tile_type_procs[GetTileType(tile)]->tile_loop_proc(tile);
 
@@ -673,11 +674,12 @@
 		} else {
 			tile = TILE_MASK(tile - TILELOOP_SIZE * (MapSizeX() / TILELOOP_SIZE - 1) + TileDiffXY(0, TILELOOP_SIZE)); /* x would overflow, also increase y */
 		}
-	} while (--count != 0);
+	} while (count && --count != 0);
+
 	assert((tile & ~TILELOOP_ASSERTMASK) == 0);
 
 	tile += 9;
-	if (tile & TILELOOP_CHKMASK) {
+	if (tile & ~TILELOOP_ASSERTMASK) {
 		tile = (tile + MapSizeX()) & TILELOOP_ASSERTMASK;
 	}
 	_cur_tileloop_tile = tile;