diff --git a/CHANGELOG.markdown b/CHANGELOG.markdown
--- a/CHANGELOG.markdown
+++ b/CHANGELOG.markdown
@@ -1,3 +1,7 @@
+3.4.1
+-----
+* Trustworthy despite UndecidableInstances
+
 3.4
 ---
 * Delegate `fail` to the underlying `Monad`, rather than `error`.
diff --git a/README.markdown b/README.markdown
--- a/README.markdown
+++ b/README.markdown
@@ -3,7 +3,7 @@
 
 [![Build Status](https://secure.travis-ci.org/ekmett/either.png?branch=master)](http://travis-ci.org/ekmett/either)
 
-This provides an either monad transformer that unlike ErrorT is unencumbered by a constraint on its left hand argument. This is needed for a number of applications of this monad transformer, notably in recursion schemes.
+This provides an `Either` monad transformer that unlike `ErrorT` is unencumbered by a constraint on its `Left` hand argument. This is needed for a number of applications of this monad transformer, notably in [recursion-schemes](https://github.com/ekmett/recursion-schemes).
 
 Contact Information
 -------------------
diff --git a/either.cabal b/either.cabal
--- a/either.cabal
+++ b/either.cabal
@@ -1,6 +1,6 @@
 name:          either
 category:      Control, Monads
-version:       3.4
+version:       3.4.1
 license:       BSD3
 cabal-version: >= 1.6
 license-file:  LICENSE
diff --git a/src/Control/Monad/Trans/Either.hs b/src/Control/Monad/Trans/Either.hs
--- a/src/Control/Monad/Trans/Either.hs
+++ b/src/Control/Monad/Trans/Either.hs
@@ -1,3 +1,8 @@
+{-# LANGUAGE CPP #-}
+#if defined(__GLASGOW_HASKELL__) && __GLASGOW_HASKELL__ >= 702
+{-# LANGUAGE Trustworthy #-}
+#endif
+
 {-# LANGUAGE FlexibleInstances     #-}
 {-# LANGUAGE FlexibleContexts      #-}
 {-# LANGUAGE UndecidableInstances  #-}