diff --git a/src/map_type.h b/src/map_type.h
--- a/src/map_type.h
+++ b/src/map_type.h
@@ -60,10 +60,10 @@ struct TileIndexDiffC {
 };
 
 /** Minimal and maximal map width and height */
-static const uint MIN_MAP_SIZE_BITS = 6;                      ///< Minimal size of map is equal to 2 ^ MIN_MAP_SIZE_BITS
-static const uint MAX_MAP_SIZE_BITS = 12;                     ///< Maximal size of map is equal to 2 ^ MAX_MAP_SIZE_BITS
-static const uint MIN_MAP_SIZE      = 1 << MIN_MAP_SIZE_BITS; ///< Minimal map size = 64
-static const uint MAX_MAP_SIZE      = 1 << MAX_MAP_SIZE_BITS; ///< Maximal map size = 4096
+static const uint MIN_MAP_SIZE_BITS = 6;                       ///< Minimal size of map is equal to 2 ^ MIN_MAP_SIZE_BITS
+static const uint MAX_MAP_SIZE_BITS = 12;                      ///< Maximal size of map is equal to 2 ^ MAX_MAP_SIZE_BITS
+static const uint MIN_MAP_SIZE      = 1U << MIN_MAP_SIZE_BITS; ///< Minimal map size = 64
+static const uint MAX_MAP_SIZE      = 1U << MAX_MAP_SIZE_BITS; ///< Maximal map size = 4096
 
 /**
  * Approximation of the length of a straight track, relative to a diagonal