diff --git a/wxPython/wxPython/lib/rcsizer.py b/wxPython/wxPython/lib/rcsizer.py
index 06c5c29ad0..482e4a7066 100644
--- a/wxPython/wxPython/lib/rcsizer.py
+++ b/wxPython/wxPython/lib/rcsizer.py
@@ -111,13 +111,13 @@ class RowColSizer(wxPySizer):
 
     #--------------------------------------------------
     def CalcMin( self ):
+        self.rowHeights = []
+        self.colWidths = []
+
         items = self.GetChildren()
         if not items:
             return wxSize(10, 10)
 
-        self.rowHeights = []
-        self.colWidths = []
-
         for item in items:
             self._add( item.CalcMin(), item.GetUserData() )