diff --git a/ubb-la/gui.c b/ubb-la/gui.c
index abd4556..bb45ad8 100644
--- a/ubb-la/gui.c
+++ b/ubb-la/gui.c
@@ -466,7 +466,7 @@ static void show_divisions(void)
 
 static int pos_step(int zoom)
 {
-	return 1 << (MAX_ZOOM-zoom+1);
+	return zoom == MAX_ZOOM ? 1 : 1 << (MAX_ZOOM-zoom+1);
 }