diff --git a/lib/tty/tty.c b/lib/tty/tty.c
index 1999deb00..68317e75e 100644
--- a/lib/tty/tty.c
+++ b/lib/tty/tty.c
@@ -179,6 +179,9 @@ tty_draw_box (int y, int x, int ys, int xs, gboolean single)
 {
     int y2, x2;
 
+    if (ys <= 0 || xs <= 0)
+        return;
+
     ys--;
     xs--;