diff --git a/tryton/gui/window/view_form/view/form_gtk/parser.py b/tryton/gui/window/view_form/view/form_gtk/parser.py
index 265bcd6641..a6a132ec4d 100644
--- a/tryton/gui/window/view_form/view/form_gtk/parser.py
+++ b/tryton/gui/window/view_form/view/form_gtk/parser.py
@@ -470,7 +470,7 @@ class ParserForm(ParserInterface):
                         gtk.gdk.PIXBUF_ROTATE_COUNTERCLOCKWISE)
                 elif CONFIG['client.form_tab'] == 'right':
                     angle = -90
-                    tab_box, image_pos = gtk.VBox(spacing=3)
+                    tab_box = gtk.VBox(spacing=3)
                     image_pos, image_rotate = ('start',
                         gtk.gdk.PIXBUF_ROTATE_CLOCKWISE)
                 else: