diff --git a/wxPython/wx/lib/calendar.py b/wxPython/wx/lib/calendar.py
index 257b8c1c45..4cb46b1b3f 100644
--- a/wxPython/wx/lib/calendar.py
+++ b/wxPython/wx/lib/calendar.py
@@ -292,6 +292,8 @@ class CalDraw:
             self.cal_days.append(str(i))
             i = i + 1
 
+        self.end_pos = dow + dim
+
         return start_pos
 
     def SetWeekEnd(self, font_color=None, backgrd = None):
@@ -540,6 +542,9 @@ class CalDraw:
         f = wx.Font(10, self.font, wx.NORMAL, self.bold)      # initial font setting
         self._CalcFontSize(DC, f)
 
+        if key > self.end_pos: 
+            key = self.end_pos
+
         val = self.cal_days[key]
         cnt_x = key % 7
         cnt_y = int(key / 7)+1