diff --git a/src/common/bookctrl.cpp b/src/common/bookctrl.cpp
index d083152210..cdd90bf2e0 100644
--- a/src/common/bookctrl.cpp
+++ b/src/common/bookctrl.cpp
@@ -145,7 +145,7 @@ wxBookCtrl::InsertPage(size_t nPage,
                        int imageId)
 {
     wxCHECK_MSG( page, false, _T("NULL page in wxBookCtrl::InsertPage()") );
-    wxCHECK_MSG( nPage < m_pages.size(), false,
+    wxCHECK_MSG( nPage <= m_pages.size(), false,
                  _T("invalid page index in wxBookCtrl::InsertPage()") );
 
     m_pages.Insert(page, nPage);