diff --git a/gui/additionsPane.py b/gui/additionsPane.py
index dd1ebf25e..8bc72f8ec 100644
--- a/gui/additionsPane.py
+++ b/gui/additionsPane.py
@@ -92,19 +92,16 @@ class AdditionsPane(TogglePanel):
     def getName(self, idx):
         return self.PANES[idx]
 
-    def toggleContent(self, event):
-        TogglePanel.toggleContent(self, event)
-        h = self.headerPanel.GetSize()[1] + 4
+    def ToggleContent(self, event):
+        TogglePanel.ToggleContent(self, event)
+        h = self.header_panel.GetSize()[1] + 4
 
         if self.IsCollapsed():
             self.old_pos = self.parent.GetSashPosition()
             self.parent.SetMinimumPaneSize(h)
             self.parent.SetSashPosition(h * -1, True)
-            # only available in >= wx2.9
-            if getattr(self.parent, "SetSashInvisible", None):
-                self.parent.SetSashInvisible(True)
+            self.parent.SetSashInvisible(True)
         else:
-            if getattr(self.parent, "SetSashInvisible", None):
-                self.parent.SetSashInvisible(False)
+            self.parent.SetSashInvisible(False)
             self.parent.SetMinimumPaneSize(200)
             self.parent.SetSashPosition(self.old_pos, True)