diff --git a/src/aui/framemanager.cpp b/src/aui/framemanager.cpp
index 0ebfccaf03..18453eb829 100644
--- a/src/aui/framemanager.cpp
+++ b/src/aui/framemanager.cpp
@@ -3537,7 +3537,7 @@ void wxAuiManager::UpdateButtonOnScreen(wxAuiDockUIPart* button_ui_part,
                                         const wxMouseEvent& event)
 {
     wxAuiDockUIPart* hit_test = HitTest(event.GetX(), event.GetY());
-    if (!hit_test)
+    if (!hit_test || !button_ui_part)
         return;
         
     int state = wxAUI_BUTTON_STATE_NORMAL;