diff --git a/examples/Agent.hs b/examples/Agent.hs
--- a/examples/Agent.hs
+++ b/examples/Agent.hs
@@ -8,22 +8,27 @@
 -- Example of how to build an agent using OpenAI.Gym.Client
 -------------------------------------------------------------------------------
 {-# LANGUAGE NamedFieldPuns #-}
+{-# LANGUAGE CPP #-}
 module Main where
 
-import Prelude
-import Control.Monad (replicateM_, when)
-import Control.Monad.Catch
-import Control.Exception.Base
+import           Control.Exception.Base
+import           Control.Monad          (replicateM_, when)
+import           Control.Monad.Catch
+import           Prelude
 
-import OpenAI.Gym
-import Servant.Client
-import Network.HTTP.Client
+import           Network.HTTP.Client
+import           OpenAI.Gym
+import           Servant.Client
 
 
 main :: IO ()
 main = do
   manager <- newManager defaultManagerSettings
+#if MIN_VERSION_servant_client(0,13,0)
+  out <- runClientM example (ClientEnv manager url Nothing)
+#else
   out <- runClientM example (ClientEnv manager url)
+#endif
   case out of
     Left err -> print err
     Right ok -> print ok
diff --git a/gym-http-api.cabal b/gym-http-api.cabal
--- a/gym-http-api.cabal
+++ b/gym-http-api.cabal
@@ -1,9 +1,11 @@
--- This file has been generated from package.yaml by hpack version 0.18.1.
+-- This file has been generated from package.yaml by hpack version 0.21.2.
 --
 -- see: https://github.com/sol/hpack
+--
+-- hash: 085a2053bc4ebb1d1451b833911deb047b05b2a99658d37c37af73e0bda7d26f
 
 name:           gym-http-api
-version:        0.1.0.0
+version:        0.1.0.1
 synopsis:       REST client to the gym-http-api project
 description:    This library provides a REST client to the gym open-source library. gym-http-api itself provides a <https://github.com/openai/gym-http-api/blob/master/gym_http_server.py python-based REST> server to the gym open-source library, allowing development in languages other than python.
                 .
@@ -33,13 +35,13 @@
       src
   default-extensions: OverloadedStrings
   build-depends:
-      base           >= 4.7 && < 5
-    , servant-client >= 0.9
-    , aeson                >= 1.0
-    , unordered-containers >= 0.2
-    , servant              >= 0.9
-    , servant-lucid        >= 0.7
-    , text                 >= 1.2
+      aeson >=1.0
+    , base >=4.7 && <5
+    , servant >=0.9
+    , servant-client >=0.9
+    , servant-lucid >=0.7
+    , text >=1.2
+    , unordered-containers >=0.2
   exposed-modules:
       OpenAI.Gym
       OpenAI.Gym.API
@@ -54,9 +56,11 @@
       examples
   default-extensions: OverloadedStrings
   build-depends:
-      base           >= 4.7 && < 5
-    , servant-client >= 0.9
+      base >=4.7 && <5
+    , exceptions >=0.8
     , gym-http-api
-    , http-client    >= 0.5
-    , exceptions     >= 0.8
+    , http-client >=0.5
+    , servant-client >=0.9
+  other-modules:
+      Paths_gym_http_api
   default-language: Haskell2010