diff --git a/include/wx/radiobox.h b/include/wx/radiobox.h
index 540e4945c3..ed60e202b8 100644
--- a/include/wx/radiobox.h
+++ b/include/wx/radiobox.h
@@ -96,6 +96,8 @@ protected:
     wxRadioBoxBase()
     {
         m_majorDim = 0;
+        m_numCols = 0;
+        m_numRows = 0;
 
 #if wxUSE_TOOLTIPS
         m_itemsTooltips = NULL;