diff --git a/hoauth2.cabal b/hoauth2.cabal
--- a/hoauth2.cabal
+++ b/hoauth2.cabal
@@ -1,6 +1,6 @@
 Name:                hoauth2
 -- http://wiki.haskell.org/Package_versioning_policy
-Version:             1.8.0
+Version:             1.8.1
 
 Synopsis:            Haskell OAuth2 authentication client
 
diff --git a/src/Network/OAuth/OAuth2/Internal.hs b/src/Network/OAuth/OAuth2/Internal.hs
--- a/src/Network/OAuth/OAuth2/Internal.hs
+++ b/src/Network/OAuth/OAuth2/Internal.hs
@@ -14,10 +14,11 @@
 import           Control.Arrow        (second)
 import           Control.Monad.Catch
 import           Data.Aeson
+import           Data.Aeson.Types (explicitParseFieldMaybe, Parser)
 import qualified Data.ByteString      as BS
 import qualified Data.ByteString.Lazy as BSL
 import           Data.Maybe
-import           Data.Text            (Text, pack)
+import           Data.Text            (Text, pack, unpack)
 import           Data.Text.Encoding
 import           GHC.Generics
 import           Lens.Micro
@@ -58,9 +59,18 @@
     , idToken      :: Maybe IdToken
     } deriving (Show, Generic)
 
+parseIntFlexible :: Value -> Parser Int
+parseIntFlexible (String s) = pure . read $ unpack s
+parseIntFlexible v = parseJSON v
+
 -- | Parse JSON data into 'OAuth2Token'
 instance FromJSON OAuth2Token where
-    parseJSON = genericParseJSON defaultOptions { fieldLabelModifier = camelTo2 '_' }
+    parseJSON = withObject "OAuth2Token" $ \v -> OAuth2Token
+        <$> v .: "access_token"
+        <*> v .:? "refresh_token"
+        <*> explicitParseFieldMaybe parseIntFlexible v "expires_in"
+        <*> v .:? "token_type"
+        <*> v .:? "id_token"
 instance ToJSON OAuth2Token where
     toJSON = genericToJSON defaultOptions { fieldLabelModifier = camelTo2 '_' }
     toEncoding = genericToEncoding defaultOptions { fieldLabelModifier = camelTo2 '_' }