diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,5 +1,9 @@
 # Revision history for transformers-eff
 
+## 0.2.1.0  -- 2018-03-21
+
+* Upper bounds have been removed. This is due to lack of maintainer time.
+
 ## 0.2.0.0  -- 2017-02-07
 
 ### Breaking Changes
diff --git a/Control/Effect/Nondeterminism.hs b/Control/Effect/Nondeterminism.hs
--- a/Control/Effect/Nondeterminism.hs
+++ b/Control/Effect/Nondeterminism.hs
@@ -35,7 +35,7 @@
 -- TODO Non-conflicting names?
 
 mzero :: Nondeterministic m => m a
-mzero = choose mempty
+mzero = choose []
 
 mplus :: Nondeterministic m => m a -> m a -> m a
 mplus l r = join (choose [l,r])
diff --git a/transformers-eff.cabal b/transformers-eff.cabal
--- a/transformers-eff.cabal
+++ b/transformers-eff.cabal
@@ -1,6 +1,6 @@
 name:                transformers-eff
 synopsis:            An approach to managing composable effects, ala mtl/transformers/extensible-effects/Eff
-version:             0.2.0.0
+version:             0.2.1.0
 homepage:            https://github.com/ocharles/transformers-eff
 license:             BSD3
 license-file:        LICENSE
@@ -17,11 +17,11 @@
   exposed-modules:     Control.Effect, Control.Effect.Environment, Control.Effect.Nondeterminism, Control.Effect.Exception, Control.Effect.IO, Control.Effect.State, Control.Effect.Identity
   -- other-modules:
   other-extensions:    TypeOperators, DeriveDataTypeable, DefaultSignatures, DeriveFunctor, StandaloneDeriving, ExistentialQuantification, FlexibleContexts, FlexibleInstances, FunctionalDependencies, KindSignatures, RankNTypes, UndecidableInstances, MultiParamTypeClasses, GeneralizedNewtypeDeriving
-  build-depends:       base >=4.8 && <5
-                     , transformers >=0.4 && <0.6
-                     , list-transformer >= 1.0.1 && < 1.1
-                     , free >= 4.12.4 && < 4.13
-                     , mmorph >= 1.0.9 && < 1.1
+  build-depends:       base >=4.8 && < 5
+                     , transformers >=0.4
+                     , list-transformer >= 1.0.1
+                     , free >= 4.12.4
+                     , mmorph >= 1.0.9
   -- hs-source-dirs:
   default-language:    Haskell2010
   ghc-options: -Wall
@@ -32,3 +32,4 @@
   main-is: Bench.hs
   type: exitcode-stdio-1.0
   ghc-options: -O2
+  default-language:    Haskell2010