diff --git a/tunnelbridge_cmd.c b/tunnelbridge_cmd.c
--- a/tunnelbridge_cmd.c
+++ b/tunnelbridge_cmd.c
@@ -228,10 +228,10 @@ int32 CmdBuildBridge(TileIndex end_tile,
 	if (x == sx) {
 		if (y == sy) return_cmd_error(STR_5008_CANNOT_START_AND_END_ON);
 		direction = AXIS_Y;
-		if (y > sy) intswap(y,sy);
+		if (y > sy) uintswap(y,sy);
 	} else if (y == sy) {
 		direction = AXIS_X;
-		if (x > sx) intswap(x,sx);
+		if (x > sx) uintswap(x,sx);
 	} else {
 		return_cmd_error(STR_500A_START_AND_END_MUST_BE_IN);
 	}