diff --git a/CHANGES.md b/CHANGES.md
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -1,6 +1,11 @@
 Changes
 =======
 
+Version 1.0.2
+-------------
+
+Fix a bug in the generic instance
+
 Version 1.0.1
 -------------
 
diff --git a/Test/SmallCheck/Property.hs b/Test/SmallCheck/Property.hs
--- a/Test/SmallCheck/Property.hs
+++ b/Test/SmallCheck/Property.hs
@@ -109,7 +109,7 @@
 --
 -- 'over' does not affect the quantification context.
 over
-  :: (Monad m, Show a, Testable m b)
+  :: (Show a, Testable m b)
   => Series m a -> (a -> b) -> Property m
 over = testFunction
 
@@ -153,7 +153,7 @@
   test = id
 
 testFunction
-  :: (Monad m, Show a, Testable m b)
+  :: (Show a, Testable m b)
   => Series m a -> (a -> b) -> Property m
 testFunction s f = Property $ reader $ \env ->
   let
diff --git a/Test/SmallCheck/Series.hs b/Test/SmallCheck/Series.hs
--- a/Test/SmallCheck/Series.hs
+++ b/Test/SmallCheck/Series.hs
@@ -27,7 +27,7 @@
              GeneralizedNewtypeDeriving, FlexibleContexts #-}
 -- The following is needed for generic instances
 {-# LANGUAGE DefaultSignatures, FlexibleContexts, TypeOperators,
-             TypeSynonymInstances, FlexibleInstances #-}
+             TypeSynonymInstances, FlexibleInstances, OverlappingInstances #-}
 
 module Test.SmallCheck.Series (
   -- {{{
@@ -306,7 +306,7 @@
 alts0 :: Series m a -> Series m a
 alts0 s = s
 
-alts1 :: (Monad m, CoSerial m a) => Series m b -> Series m (a->b)
+alts1 :: CoSerial m a => Series m b -> Series m (a->b)
 alts1 rs =
   decDepthChecked (constM rs) (coseries rs)
 
@@ -333,7 +333,7 @@
     (coseries $ coseries $ coseries $ coseries rs)
 
 -- | Same as 'alts1', but preserves the depth.
-newtypeAlts :: (Monad m, CoSerial m a) => Series m b -> Series m (a->b)
+newtypeAlts :: CoSerial m a => Series m b -> Series m (a->b)
 newtypeAlts = coseries
 
 -- }}}
@@ -363,7 +363,7 @@
   {-# INLINE gCoseries #-}
 
 instance GSerial m U1 where
-  gSeries = cons0 U1
+  gSeries = pure U1
   {-# INLINE gSeries #-}
 instance GCoSerial m U1 where
   gCoseries rs = constM rs
@@ -391,6 +391,9 @@
       R1 y -> g y
   {-# INLINE gCoseries #-}
 
+instance GSerial m f => GSerial m (C1 c f) where
+  gSeries = M1 <$> decDepth gSeries
+  {-# INLINE gSeries #-}
 -- }}}
 
 ------------------------------
@@ -465,19 +468,19 @@
     coseries rs >>- \f ->
     return $ \c -> f (N (fromEnum c - fromEnum 'a'))
 
-instance (Monad m, Serial m a, Serial m b) => Serial m (a,b) where
+instance (Serial m a, Serial m b) => Serial m (a,b) where
   series = cons2 (,)
-instance (Monad m, CoSerial m a, CoSerial m b) => CoSerial m (a,b) where
+instance (CoSerial m a, CoSerial m b) => CoSerial m (a,b) where
   coseries rs = uncurry <$> alts2 rs
 
-instance (Monad m, Serial m a, Serial m b, Serial m c) => Serial m (a,b,c) where
+instance (Serial m a, Serial m b, Serial m c) => Serial m (a,b,c) where
   series = cons3 (,,)
-instance (Monad m, CoSerial m a, CoSerial m b, CoSerial m c) => CoSerial m (a,b,c) where
+instance (CoSerial m a, CoSerial m b, CoSerial m c) => CoSerial m (a,b,c) where
   coseries rs = uncurry3 <$> alts3 rs
 
-instance (Monad m, Serial m a, Serial m b, Serial m c, Serial m d) => Serial m (a,b,c,d) where
+instance (Serial m a, Serial m b, Serial m c, Serial m d) => Serial m (a,b,c,d) where
   series = cons4 (,,,)
-instance (Monad m, CoSerial m a, CoSerial m b, CoSerial m c, CoSerial m d) => CoSerial m (a,b,c,d) where
+instance (CoSerial m a, CoSerial m b, CoSerial m c, CoSerial m d) => CoSerial m (a,b,c,d) where
   coseries rs = uncurry4 <$> alts4 rs
 
 instance Monad m => Serial m Bool where
@@ -488,15 +491,15 @@
     rs >>- \r2 ->
     return $ \x -> if x then r1 else r2
 
-instance (Monad m, Serial m a) => Serial m (Maybe a) where
+instance (Serial m a) => Serial m (Maybe a) where
   series = cons0 Nothing \/ cons1 Just
-instance (Monad m, CoSerial m a) => CoSerial m (Maybe a) where
+instance (CoSerial m a) => CoSerial m (Maybe a) where
   coseries rs =
     maybe <$> alts0 rs <~> alts1 rs
 
-instance (Monad m, Serial m a, Serial m b) => Serial m (Either a b) where
+instance (Serial m a, Serial m b) => Serial m (Either a b) where
   series = cons1 Left \/ cons1 Right
-instance (Monad m, CoSerial m a, CoSerial m b) => CoSerial m (Either a b) where
+instance (CoSerial m a, CoSerial m b) => CoSerial m (Either a b) where
   coseries rs =
     either <$> alts1 rs <~> alts1 rs
 
@@ -508,11 +511,11 @@
     alts2 rs >>- \f ->
     return $ \xs -> case xs of [] -> y; x:xs' -> f x xs'
 
-instance (CoSerial m a, Serial m b, Monad m) => Serial m (a->b) where
+instance (CoSerial m a, Serial m b) => Serial m (a->b) where
   series = coseries series
 -- Thanks to Ralf Hinze for the definition of coseries
 -- using the nest auxiliary.
-instance (Serial m a, CoSerial m a, Serial m b, CoSerial m b, Monad m) => CoSerial m (a->b) where
+instance (Serial m a, CoSerial m a, Serial m b, CoSerial m b) => CoSerial m (a->b) where
   coseries r = do
     args <- unwind series
 
diff --git a/smallcheck.cabal b/smallcheck.cabal
--- a/smallcheck.cabal
+++ b/smallcheck.cabal
@@ -1,5 +1,5 @@
 Name:          smallcheck
-Version:       1.0.1
+Version:       1.0.2
 Cabal-Version: >= 1.6
 License:       BSD3
 License-File:  LICENSE
@@ -27,7 +27,7 @@
 Source-repository this
   type:     git
   location: git://github.com/feuerbach/smallcheck.git
-  tag:      v1.0.1
+  tag:      v1.0.2
 
 Library