diff --git a/ubb-la/gui.c b/ubb-la/gui.c
index 117a30b..5dc5dec 100644
--- a/ubb-la/gui.c
+++ b/ubb-la/gui.c
@@ -175,7 +175,7 @@ static void textf(int x, int y, uint32_t color, const char *fmt, ...)
 static void show_map(int skip, int nibbles, int s0, int s1)
 {
 	int w = nibbles-skip;
-	int m = (nibbles+skip) >> 1;
+	int m = (nibbles-skip) >> 1;
 	int scale = 0;
 	int x0, x1;