diff --git a/src/mac/carbon/dcclient.cpp b/src/mac/carbon/dcclient.cpp
index 27164c2c9e..f50ec02f4c 100644
--- a/src/mac/carbon/dcclient.cpp
+++ b/src/mac/carbon/dcclient.cpp
@@ -258,6 +258,7 @@ wxClientDC::wxClientDC()
 wxClientDC::wxClientDC(wxWindow *window) :
     wxWindowDC( window )
 {
+    wxCHECK_RET( window, _T("invalid window in wxClientDC") );
     wxPoint origin = window->GetClientAreaOrigin() ;
     m_window->GetClientSize( &m_width , &m_height);
     SetDeviceOrigin( origin.x, origin.y );
@@ -266,6 +267,7 @@ wxClientDC::wxClientDC(wxWindow *window) :
 #else
 wxClientDC::wxClientDC(wxWindow *window)
 {
+    wxCHECK_RET( window, _T("invalid window in wxClientDC") );
     m_window = window ;
     wxTopLevelWindowMac* rootwindow = window->MacGetTopLevelWindow() ;
     if (!rootwindow)