diff --git a/etg/object.py b/etg/object.py
index d3388664..cecfff09 100644
--- a/etg/object.py
+++ b/etg/object.py
@@ -81,24 +81,8 @@ def run():
         doc='Deletes the C++ object this Python object is a proxy for.',
         transferThis=True)  # TODO: Check this
         
-    # Teach SIP how to convert to specific class types
-    c.addItem(etgtools.WigCode("""\
-    %ConvertToSubClassCode
-        const wxClassInfo* info   = sipCpp->GetClassInfo();
-        wxString           name   = info->GetClassName();
-        bool               exists = sipFindType(name) != NULL;
-        while (info && !exists) {
-            info = info->GetBaseClass1();
-            name = info->GetClassName();
-            exists = sipFindType(name) != NULL;
-        }
-        if (info) 
-            sipType = sipFindType(name);
-        else
-            sipType = NULL;
-    %End
-    """))
-              
+        
+    tools.addSipConvertToSubClassCode(c)
               
     #-----------------------------------------------------------------
     tools.doCommonTweaks(module)
diff --git a/etg/window.py b/etg/window.py
index 57134067..4c69e329 100644
--- a/etg/window.py
+++ b/etg/window.py
@@ -249,6 +249,7 @@ def run():
     ##c.addProperty('GtkWidget GetGtkWidget')
 
     tools.fixWindowClass(c)
+    tools.addSipConvertToSubClassCode(c)
 
     # for compatibility with Classic
     c.addPyMethod('GetPositionTuple', '(self)', 'return self.GetPosition()', deprecated=True)
diff --git a/etgtools/tweaker_tools.py b/etgtools/tweaker_tools.py
index 6f17ca0d..169466c9 100644
--- a/etgtools/tweaker_tools.py
+++ b/etgtools/tweaker_tools.py
@@ -275,6 +275,27 @@ def addWindowVirtuals(klass):
     klass.addItem(extractors.WigCode(txt))
     klass.addPublic()
                   
+                  
+def addSipConvertToSubClassCode(klass):
+    """
+    Teach SIP how to convert to specific subclass types
+    """
+    klass.addItem(extractors.WigCode("""\
+    %ConvertToSubClassCode
+        const wxClassInfo* info   = sipCpp->GetClassInfo();
+        wxString           name   = info->GetClassName();
+        bool               exists = sipFindType(name) != NULL;
+        while (info && !exists) {
+            info = info->GetBaseClass1();
+            name = info->GetClassName();
+            exists = sipFindType(name) != NULL;
+        }
+        if (info) 
+            sipType = sipFindType(name);
+        else
+            sipType = NULL;
+    %End
+    """))
     
     
 def getEtgFiles(names):