diff --git a/table/autorail.h b/table/autorail.h
--- a/table/autorail.h
+++ b/table/autorail.h
@@ -50,7 +50,7 @@ const int AutorailTilehSprite[31][6] = {
 
 // maps each pixel of a tile (16x16) to a selection type
 // (0,0) is the top corner, (16,16) the bottom corner
-const int AutorailPiece[16][16] = {
+const byte AutorailPiece[16][16] = {
 	{ 2, 2, 2, 2, 2, 2, 0, 0, 0, 0, 5, 5, 5, 5, 5, 5 },
 	{ 2, 2, 2, 2, 2, 2, 0, 0, 0, 0, 5, 5, 5, 5, 5, 5 },
 	{ 2, 2, 2, 2, 2, 2, 0, 0, 0, 0, 5, 5, 5, 5, 5, 5 },
diff --git a/viewport.c b/viewport.c
--- a/viewport.c
+++ b/viewport.c
@@ -1875,7 +1875,7 @@ void SetTileSelectBigSize(int ox, int oy
 /* returns the best autorail highlight type from map coordinates */
 static byte GetAutorailHT(int x, int y)
 {
-	int i;
+	byte i;
 	i = AutorailPiece[x&0xF][y&0xF];
 	return HT_RAIL | i;
 }