diff --git a/samples/treectrl/treetest.cpp b/samples/treectrl/treetest.cpp
index ff584dbaf6..38bf36bcc6 100644
--- a/samples/treectrl/treetest.cpp
+++ b/samples/treectrl/treetest.cpp
@@ -748,7 +748,7 @@ void MyFrame::OnToggleAlternateStates(wxCommandEvent& WXUNUSED(event))
 
 void MyFrame::OnToggleButtons(wxCommandEvent& WXUNUSED(event))
 {
-#if USE_GENERIC_TREECTRL || !defined(__WXMSW__)
+#ifdef HAS_GENERIC_TREECTRL
     if ( wxGetApp().ShowButtons() )
     {
         m_treeCtrl->CreateButtonsImageList(-1);
@@ -1064,9 +1064,9 @@ void MyTreeCtrl::CreateStateImageList(bool del)
     AssignStateImageList(states);
 }
 
-#if USE_GENERIC_TREECTRL || (!defined(__WXMSW__) && !defined(__WXQT__))
 void MyTreeCtrl::CreateButtonsImageList(int size)
 {
+#ifdef HAS_GENERIC_TREECTRL
     if ( size == -1 )
     {
         SetButtonsImageList(NULL);
@@ -1112,8 +1112,7 @@ void MyTreeCtrl::CreateButtonsImageList(int size)
 
     AssignButtonsImageList(images);
 #else
-void MyTreeCtrl::CreateButtonsImageList(int WXUNUSED(size))
-{
+    wxUnusedVar(size);
 #endif
 }
 
diff --git a/samples/treectrl/treetest.h b/samples/treectrl/treetest.h
index 43439ea8d5..865a39d1fa 100644
--- a/samples/treectrl/treetest.h
+++ b/samples/treectrl/treetest.h
@@ -8,6 +8,8 @@
 // Licence:     wxWindows licence
 /////////////////////////////////////////////////////////////////////////////
 
+// This can be defined to 1 to force using wxGenericTreeCtrl even on the
+// platforms where the native controls would normally be used (wxMSW and wxQt).
 #define USE_GENERIC_TREECTRL 0
 
 #if USE_GENERIC_TREECTRL
@@ -18,6 +20,13 @@
 #endif
 #endif
 
+// This one is defined if we're actually using the generic control, either
+// because it was explicitly requested above or because there is no other one
+// on this platform anyhow.
+#if USE_GENERIC_TREECTRL || (!defined(__WXMSW__) && !defined(__WXQT__))
+    #define HAS_GENERIC_TREECTRL
+#endif
+
 // Define a new application type
 class MyApp : public wxApp
 {