diff --git a/gramps/gui/widgets/multitreeview.py b/gramps/gui/widgets/multitreeview.py
index bdd40b76c..a7a2644c3 100644
--- a/gramps/gui/widgets/multitreeview.py
+++ b/gramps/gui/widgets/multitreeview.py
@@ -45,18 +45,18 @@ class MultiTreeView(Gtk.TreeView):
         self.connect('key_press_event', self.key_press_event)
         self.defer_select = False
 
-    __grid_lines_remove_vertical = {
-        Gtk.TreeViewGridLines.NONE : Gtk.TreeViewGridLines.NONE,
-        Gtk.TreeViewGridLines.HORIZONTAL : Gtk.TreeViewGridLines.HORIZONTAL,
-        Gtk.TreeViewGridLines.VERTICAL : Gtk.TreeViewGridLines.NONE,
-        Gtk.TreeViewGridLines.BOTH : Gtk.TreeViewGridLines.HORIZONTAL
-    }
-    def set_grid_lines(self, grid_lines):
-        if (self.get_direction() == Gtk.TextDirection.RTL and
-            (Gtk.get_major_version(), Gtk.get_minor_version()) < (3, 8)):
-            # Work around a gtk RTL bug, see #6871
-            grid_lines = MultiTreeView.__grid_lines_remove_vertical[grid_lines]
-        super(MultiTreeView, self).set_grid_lines(grid_lines)
+    if (Gtk.get_major_version(), Gtk.get_minor_version()) < (3, 8):
+        __grid_lines_remove_vertical = {
+            Gtk.TreeViewGridLines.NONE : Gtk.TreeViewGridLines.NONE,
+            Gtk.TreeViewGridLines.HORIZONTAL : Gtk.TreeViewGridLines.HORIZONTAL,
+            Gtk.TreeViewGridLines.VERTICAL : Gtk.TreeViewGridLines.NONE,
+            Gtk.TreeViewGridLines.BOTH : Gtk.TreeViewGridLines.HORIZONTAL
+        }
+        def set_grid_lines(self, grid_lines):
+            if self.get_direction() == Gtk.TextDirection.RTL:
+                # Work around a gtk RTL bug, see #6871
+                grid_lines = MultiTreeView.__grid_lines_remove_vertical[grid_lines]
+            super(MultiTreeView, self).set_grid_lines(grid_lines)
 
     def key_press_event(self, widget, event):
         if event.type == Gdk.EventType.KEY_PRESS: