diff --git a/lib/goban.py b/lib/goban.py
index 6b96a09..e3488b1 100644
--- a/lib/goban.py
+++ b/lib/goban.py
@@ -99,6 +99,9 @@ class Goban:
     def set_hover(self, pos):
         realpos = _real_pos(pos)
         
+        if _i(realpos) < 0 or _i(realpos) > 18 or _j(realpos) < 0 or _j(realpos) > 18:
+            return
+
         if self.hover == realpos:
             return
 
@@ -136,7 +139,7 @@ class Goban:
         board = p.in_dll(Goban.libboard, 'board')
 
         for pos in range(421):
-            if _i(pos) < 0 or _j(pos) < 0:
+            if _i(pos) < 0 or _i(pos) > 18 or _j(pos) < 0 or _j(pos) > 18:
                 continue
 
             code = self._get_draw_code(pos, board[pos])