diff --git a/src/disaster_cmd.cpp b/src/disaster_cmd.cpp
index 98cfe86928..87002eb247 100644
--- a/src/disaster_cmd.cpp
+++ b/src/disaster_cmd.cpp
@@ -885,7 +885,7 @@ static void Disaster_Submarine_Init(DisasterSubType subtype)
 	int x = TileX(r) * TILE_SIZE + TILE_SIZE / 2;
 
 	if (HasBit(r, 31)) {
-		y = MapMaxX() * TILE_SIZE - TILE_SIZE / 2 - 1;
+		y = MapMaxY() * TILE_SIZE - TILE_SIZE / 2 - 1;
 		dir = DIR_NW;
 	} else {
 		y = TILE_SIZE / 2;