diff --git a/src/motif/scrolbar.cpp b/src/motif/scrolbar.cpp
index 5b19681cf3..6cbdf29c23 100644
--- a/src/motif/scrolbar.cpp
+++ b/src/motif/scrolbar.cpp
@@ -125,6 +125,8 @@ static void wxScrollBarCallback(Widget widget, XtPointer clientData,
                                 XmScaleCallbackStruct *cbs)
 {
     wxScrollBar *scrollBar = (wxScrollBar*)wxGetWindowFromTable(widget);
+    wxCHECK_RET( scrollBar, _T("invalid widget in scrollbar callback") );
+
     wxOrientation orientation = (wxOrientation)wxPtrToUInt(clientData);
     wxEventType eventType = wxEVT_NULL;
 
diff --git a/src/motif/window.cpp b/src/motif/window.cpp
index 66428802a9..a99a8bb706 100644
--- a/src/motif/window.cpp
+++ b/src/motif/window.cpp
@@ -2088,6 +2088,8 @@ static void wxScrollBarCallback(Widget scrollbar,
                                 XmScrollBarCallbackStruct *cbs)
 {
     wxWindow *win = wxGetWindowFromTable(scrollbar);
+    wxCHECK_RET( win, _T("invalid widget in scrollbar callback") );
+
     wxOrientation orientation = (wxOrientation)wxPtrToUInt(clientData);
 
     wxEventType eventType = wxEVT_NULL;