diff --git a/kwant/lattice.py b/kwant/lattice.py
index c6ee11d6899f8a7b634fff6cc574ef21f97cedc8..cbf700d079ca11fb3def36e4c66f5415033ec204 100644
--- a/kwant/lattice.py
+++ b/kwant/lattice.py
@@ -673,9 +673,6 @@ class TranslationalSymmetry(builder.Symmetry):
             return (builder.Site(a.family, a.tag + delta, True),
                     builder.Site(b.family, b.tag + delta2, True))
 
-    def to_fd(self, a, b=None):
-        return self.act(-self.which(a), a, b)
-
     def reversed(self):
         """Return a reversed copy of the symmetry.