diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -24,6 +24,4 @@
 
 ## Status
 
-This library is at a quite early stage. It works for my use case at the moment and I will fix bugs when they come along. Also PRs for more `PSType`s definitions and bridges are very welcome!
-
-Expect bugs - especially for more advanced use cases. Although I have tested the most advanced one already with no issues, bugs always creep in.
+It works for my use case and is used in production. PRs for more `PSType`s definitions and bridges are very welcome! 
diff --git a/purescript-bridge.cabal b/purescript-bridge.cabal
--- a/purescript-bridge.cabal
+++ b/purescript-bridge.cabal
@@ -10,7 +10,7 @@
 -- PVP summary:      +-+------- breaking API changes
 --                   | | +----- non-breaking API additions
 --                   | | | +--- code changes with no API change
-version:             0.7.0.1
+version:             0.8.0.0
 
 -- A short (one-line) description of the package.
 synopsis:            Generate PureScript data types from Haskell data types
@@ -70,7 +70,7 @@
   -- other-extensions:
 
   -- Other library packages from which modules are imported.
-  build-depends:       base >=4.8 && <= 5.1
+  build-depends:       base >=4.8 && < 6.0
                      , containers
                      , directory
                      , filepath
diff --git a/src/Language/PureScript/Bridge/Printer.hs b/src/Language/PureScript/Bridge/Printer.hs
--- a/src/Language/PureScript/Bridge/Printer.hs
+++ b/src/Language/PureScript/Bridge/Printer.hs
@@ -50,11 +50,8 @@
 sumTypesToNeededPackages = Set.unions . map sumTypeToNeededPackages
 
 sumTypeToNeededPackages :: SumType lang -> Set Text
-sumTypeToNeededPackages st = let
-    types = getUsedTypes st
-    packages = filter (not . T.null) . map _typePackage $ types
-  in
-    Set.fromList packages
+sumTypeToNeededPackages st =
+  Set.filter (not . T.null) . Set.map _typePackage $ getUsedTypes st
 
 moduleToText :: Module 'PureScript -> Text
 moduleToText m = T.unlines $
@@ -71,10 +68,23 @@
     typeList = T.intercalate ", " (Set.toList (importTypes l))
 
 sumTypeToText :: SumType 'PureScript -> Text
-sumTypeToText (SumType t cs) = T.unlines $
+sumTypeToText st@(SumType t cs) = T.unlines $
     "data " <> typeInfoToText True t <> " ="
   : "    " <> T.intercalate "\n  | " (map (constructorToText 4) cs)
-  : [ "\nderive instance generic" <> _typeName t <> " :: Generic " <> _typeName t ]
+  : [ "\nderive instance generic" <> _typeName t <> " :: " <> genericConstrains <> genericInstance t ]
+  where
+    genericInstance = ("Generic " <>) . typeInfoToText False
+    genericConstrains
+        | stpLength == 0 = mempty
+        | otherwise = (<> " => ") $
+            if stpLength == 1
+                then genericConstrainsInner
+                else bracketWrap genericConstrainsInner
+    genericConstrainsInner = T.intercalate ", " $ map genericInstance sumTypeParameters
+    stpLength = length sumTypeParameters
+    bracketWrap x = "(" <> x <> ")"
+    sumTypeParameters = filter isTypeParam . Set.toList $ getUsedTypes st
+    isTypeParam typ = _typeName typ `elem` map _typeName (_typeParameters t)
 
 
 constructorToText :: Int -> DataConstructor 'PureScript -> Text
@@ -120,11 +130,11 @@
       }
     dropSelf = Map.delete (_typeModule t)
 
-typesToImportLines :: ImportLines -> [PSType] -> ImportLines
+typesToImportLines :: ImportLines -> Set PSType -> ImportLines
 typesToImportLines = foldr typeToImportLines
 
 typeToImportLines :: PSType -> ImportLines -> ImportLines
-typeToImportLines t ls = typesToImportLines (update ls) (_typeParameters t)
+typeToImportLines t ls = typesToImportLines (update ls) (Set.fromList (_typeParameters t))
   where
     update = if not (T.null (_typeModule t))
                 then Map.alter (Just . updateLine) (_typeModule t)
diff --git a/src/Language/PureScript/Bridge/SumType.hs b/src/Language/PureScript/Bridge/SumType.hs
--- a/src/Language/PureScript/Bridge/SumType.hs
+++ b/src/Language/PureScript/Bridge/SumType.hs
@@ -15,7 +15,7 @@
 , DataConstructor (..)
 , RecordEntry (..)
 , getUsedTypes
-, constructorToType
+, constructorToTypes
 , sigConstructor
 , sigValues
 , sumTypeInfo
@@ -24,10 +24,12 @@
 , recValue
 ) where
 
-import           Control.Lens                        hiding (from, to)
+import           Control.Lens      hiding (from, to)
 import           Data.Proxy
-import           Data.Text                           (Text)
-import qualified Data.Text                           as T
+import           Data.Set          (Set)
+import qualified Data.Set          as Set
+import           Data.Text         (Text)
+import qualified Data.Text         as T
 import           Data.Typeable
 import           Generics.Deriving
 
@@ -102,12 +104,18 @@
       }
     ]
 
-getUsedTypes :: SumType lang -> [TypeInfo lang]
-getUsedTypes (SumType _ cs) = foldr constructorToType [] cs
+-- | Get all used types in a sum type.
+--
+--   This includes all types found at the right hand side of a sum type
+--   definition, not the type parameters of the sum type itself
+getUsedTypes :: SumType lang -> Set (TypeInfo lang)
+getUsedTypes (SumType _ cs) = foldr constructorToTypes Set.empty cs
 
-constructorToType :: DataConstructor lang -> [TypeInfo lang] -> [TypeInfo lang]
-constructorToType (DataConstructor _ (Left myTs)) ts = concatMap flattenTypeInfo myTs ++ ts
-constructorToType (DataConstructor _ (Right rs))  ts = concatMap (flattenTypeInfo . _recValue) rs ++ ts
+constructorToTypes :: DataConstructor lang -> Set (TypeInfo lang) -> Set (TypeInfo lang)
+constructorToTypes (DataConstructor _ (Left myTs)) ts =
+  Set.fromList (concatMap flattenTypeInfo myTs) `Set.union` ts
+constructorToTypes (DataConstructor _ (Right rs))  ts =
+  Set.fromList (concatMap (flattenTypeInfo . _recValue) rs) `Set.union` ts
 
 -- Lenses:
 makeLenses ''DataConstructor
diff --git a/test/Spec.hs b/test/Spec.hs
--- a/test/Spec.hs
+++ b/test/Spec.hs
@@ -1,10 +1,10 @@
+{-# LANGUAGE CPP                   #-}
 {-# LANGUAGE DataKinds             #-}
 {-# LANGUAGE FlexibleInstances     #-}
 {-# LANGUAGE MultiParamTypeClasses #-}
 {-# LANGUAGE OverloadedStrings     #-}
 {-# LANGUAGE RankNTypes            #-}
 {-# LANGUAGE TypeSynonymInstances  #-}
-{-# LANGUAGE CPP #-}
 
 module Main where
 
@@ -14,7 +14,8 @@
 import qualified Data.Text                                 as T
 import           Language.PureScript.Bridge
 import           Language.PureScript.Bridge.TypeParameters
-import           Test.Hspec                                (Spec, hspec, describe, it)
+import           Test.Hspec                                (Spec, describe,
+                                                            hspec, it)
 import           Test.Hspec.Expectations.Pretty
 
 import           TestData
@@ -53,7 +54,7 @@
                 ]
        in bst `shouldBe` st
     it "tests the generation of a whole (dummy) module" $
-      let advanced = bridgeSumType (buildBridge defaultBridge) (mkSumType (Proxy :: Proxy (Bar A B M1)))
+      let advanced = bridgeSumType (buildBridge defaultBridge) (mkSumType (Proxy :: Proxy (Bar A B M1 C)))
           modules = sumTypeToModule advanced Map.empty
           m = head . map moduleToText . Map.elems $ modules
           txt = T.unlines [ "-- File auto generated by purescript-bridge! --"
@@ -65,7 +66,7 @@
                           , "import Data.Generic (class Generic)"
                           , ""
                           , ""
-                          , "data Bar a b m ="
+                          , "data Bar a b m c ="
                           , "    Bar1 (Maybe a)"
                           , "  | Bar2 (Either a b)"
                           , "  | Bar3 a"
@@ -73,7 +74,7 @@
                           , "      myMonadicResult :: m b"
                           , "    }"
                           , ""
-                          , "derive instance genericBar :: Generic Bar"
+                          , "derive instance genericBar :: (Generic a, Generic b, Generic (m b)) => Generic (Bar a b m c)"
                           , ""
                           ]
       in m `shouldBe` txt
diff --git a/test/TestData.hs b/test/TestData.hs
--- a/test/TestData.hs
+++ b/test/TestData.hs
@@ -10,9 +10,9 @@
 module TestData where
 
 import           Data.Proxy
-import           Data.Text                                 (Text)
+import           Data.Text                          (Text)
 import           Data.Typeable
-import           GHC.Generics                              (Generic)
+import           GHC.Generics                       (Generic)
 import           Language.PureScript.Bridge
 import           Language.PureScript.Bridge.PSTypes
 
@@ -40,9 +40,9 @@
           | TestVoid
           deriving (Generic, Typeable, Show)
 
-data Bar a b m = Bar1 (Maybe a) | Bar2 (Either a b) | Bar3 a
-               | Bar4 { myMonadicResult :: m b }
-               deriving (Generic, Typeable, Show)
+data Bar a b m c = Bar1 (Maybe a) | Bar2 (Either a b) | Bar3 a
+                 | Bar4 { myMonadicResult :: m b }
+                 deriving (Generic, Typeable, Show)
 
 
 a :: HaskellType