diff --git a/CHANGELOG.markdown b/CHANGELOG.markdown
--- a/CHANGELOG.markdown
+++ b/CHANGELOG.markdown
@@ -1,3 +1,7 @@
+4.0
+---
+* Updated dependencies.
+
 3.4.2
 -----
 * Added 'Data.Either.Combinators'.
diff --git a/either.cabal b/either.cabal
--- a/either.cabal
+++ b/either.cabal
@@ -1,6 +1,6 @@
 name:          either
 category:      Control, Monads
-version:       3.4.2
+version:       4.0
 license:       BSD3
 cabal-version: >= 1.6
 license-file:  LICENSE
@@ -31,7 +31,7 @@
     MonadRandom   == 0.1.*,
     mtl           >= 2.0     && < 2.2,
     semigroups    >= 0.8.3.1 && < 1,
-    semigroupoids >= 3       && < 4,
+    semigroupoids >= 4       && < 5,
     transformers  >= 0.2     && < 0.4
 
   extensions: CPP