diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -1,6 +1,6 @@
-# Google-oauth-jwt [![Build Status](https://travis-ci.org/MichelBoucey/google-oauth2-jwt.svg?branch=master)](https://travis-ci.org/MichelBoucey/google-oauth2-jwt)
+# Google-oauth2-jwt [![Build Status](https://travis-ci.org/MichelBoucey/google-oauth2-jwt.svg?branch=master)](https://travis-ci.org/MichelBoucey/google-oauth2-jwt)
 
-Google-oauth-jwt implements the creation of the signed JWT for Google Service Accounts,
+Google-oauth2-jwt implements the creation of the signed JWT for Google Service Accounts,
 to make authorized calls to Google APIs from server to server. All details here:
 
 - [https://developers.google.com/identity/protocols/OAuth2ServiceAccount](https://developers.google.com/identity/protocols/OAuth2ServiceAccount)
diff --git a/google-oauth2-jwt.cabal b/google-oauth2-jwt.cabal
--- a/google-oauth2-jwt.cabal
+++ b/google-oauth2-jwt.cabal
@@ -1,5 +1,5 @@
 name:                google-oauth2-jwt
-version:             0.1.2.1
+version:             0.1.3
 synopsis:            Get a signed JWT for Google Service Accounts
 description:         Please see README.md
 homepage:            https://github.com/MichelBoucey/google-oauth2-jwt
@@ -17,12 +17,13 @@
   hs-source-dirs:   src
   exposed-modules:  Network.Google.OAuth2.JWT
   build-depends:    base >= 4.7 && < 5
-                  , base64-bytestring >= 1.0.0.1
-                  , bytestring >= 0.10.6.0
-                  , HsOpenSSL >= 0.11.1.1
-                  , RSA >= 2.2.0
-                  , text >= 1.2.2.0
-                  , unix-time >= 0.3.6
+                  , base64-bytestring   >= 1.0.0 && < 1.1
+                  , bytestring          >= 0.10.6 && < 0.11
+                  , HsOpenSSL           >= 0.11.1.1 && < 0.12
+                  , RSA                 >= 2.1.0.3 && < 2.3
+                  , text                >= 1.2.2 && < 1.3
+                  , unix-time           >= 0.3.6 && < 0.4
+
   default-language: Haskell2010
   GHC-options:      -Wall
 
diff --git a/src/Network/Google/OAuth2/JWT.hs b/src/Network/Google/OAuth2/JWT.hs
--- a/src/Network/Google/OAuth2/JWT.hs
+++ b/src/Network/Google/OAuth2/JWT.hs
@@ -84,29 +84,27 @@
              -- Google API Console.
              -> IO (Either String B.ByteString)
              -- ^ Either an error message or a signed JWT.
-getSignedJWT iss msub scopes met privateKey = do
-  let et = fromIntegral $ fromMaybe 3600 met
-  if et >= 1 && et <= 3600
+getSignedJWT iss msub scs mxt pk = do
+  let xt = fromIntegral (fromMaybe 3600 mxt)
+  if xt >= 1 && xt <= 3600
     then do
-      cs <-
-        jwtClaimsSet
-          (maybe T.empty (\s -> "\"sub\":\"" <> s <> "\",") msub) et
+      cs <- do
+        let s = maybe T.empty (\e -> "\"sub\":\"" <> e <> "\",") msub
+        (t',xt') <- getUnixTime >>=
+          \t -> return (toText (utSeconds t),toText (utSeconds t + CTime xt))
+        return $
+          toJWT $
+            "{\"iss\":\"" <> iss <> "\"," <> s <> "\"scope\":\"" <>
+            T.intercalate " " scs <> "\",\"aud\":\"https://www.goo\
+            \gleapis.com/oauth2/v4/token\",\"exp\":" <> xt' <> ",\"\
+            \iat\":" <> t' <> "}"
       let i = toJWT "{\"alg\":\"RS256\",\"typ\":\"JWT\"}" <> "." <> cs
       return $
-        case rsassa_pkcs1_v1_5_sign hashSHA256 privateKey (fromStrict i) of
+        case rsassa_pkcs1_v1_5_sign hashSHA256 pk (fromStrict i) of
           Right s -> Right (i <> "." <> encode (toStrict s))
           Left _  -> Left "RSAError"
     else fail "Bad expiration time"
   where
-    jwtClaimsSet s e = do
-      (exp',iat') <- getUnixTime >>=
-        \t -> return (toText (utSeconds t + CTime e),toText (utSeconds t))
-      return $
-        toJWT $
-          "{\"iss\":\"" <> iss <> "\"," <> s <> "\"scope\":\""
-          <> T.intercalate " " scopes <> "\",\"aud\":\"https:\
-          \//www.googleapis.com/oauth2/v4/token\",\"exp\":" <>
-          exp' <> ",\"iat\":" <> iat' <> "}"
     toText = T.pack . show
     toJWT = encode . encodeUtf8