diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+4.3.15
+
+* Build against `ghc-9.0`
+
 4.3.14
 
 * Add `mapMaybe` and `wither`, and more laws for `filter` and `filterM`.
diff --git a/pipes.cabal b/pipes.cabal
--- a/pipes.cabal
+++ b/pipes.cabal
@@ -1,5 +1,5 @@
 Name: pipes
-Version: 4.3.14
+Version: 4.3.15
 Cabal-Version: >= 1.10
 Build-Type: Simple
 Tested-With: GHC == 7.10.3, GHC == 8.0.2, GHC == 8.2.2, GHC == 8.4.4, GHC == 8.6.5, GHC == 8.8.1
@@ -77,8 +77,8 @@
 
     Build-Depends:
         base      >= 4.4     && < 5  ,
-        criterion >= 1.1.1.0 && < 1.5,
-        optparse-applicative >= 0.12 && < 0.15,
+        criterion >= 1.1.1.0 && < 1.6,
+        optparse-applicative >= 0.12 && < 0.17,
         mtl       >= 2.1     && < 2.3,
         pipes
 
@@ -108,8 +108,8 @@
 
     Build-Depends:
         base                 >= 4.4     && < 5   ,
-        criterion            >= 1.1.1.0 && < 1.5 ,
-        optparse-applicative >= 0.12    && < 0.15,
+        criterion            >= 1.1.1.0 && < 1.6 ,
+        optparse-applicative >= 0.12    && < 0.17,
         mtl                  >= 2.1     && < 2.3 ,
         pipes                                    ,
         transformers         >= 0.2.0.0 && < 0.6
diff --git a/src/Pipes.hs b/src/Pipes.hs
--- a/src/Pipes.hs
+++ b/src/Pipes.hs
@@ -134,10 +134,11 @@
 {-| Produce a value
 
 @
-'yield' :: 'Monad' m => a -> 'Pipe' x a m ()
+'yield' :: 'Monad' m => a -> 'Producer' a m ()
+'yield' :: 'Monad' m => a -> 'Pipe'   x a m ()
 @
 -}
-yield :: Functor m => a -> Producer' a m ()
+yield :: Functor m => a -> Proxy x' x () a m ()
 yield = respond
 {-# INLINABLE [1] yield #-}
 
@@ -635,8 +636,13 @@
         Pure    r    -> return (Left r)
 {-# INLINABLE next #-}
 
--- | Convert a 'F.Foldable' to a 'Producer'
-each :: (Functor m, Foldable f) => f a -> Producer' a m ()
+{-| Convert a 'F.Foldable' to a 'Producer'
+
+@
+'each' :: ('Functor' m, 'Foldable' f) => f a -> 'Producer' a m ()
+@
+-}
+each :: (Functor m, Foldable f) => f a -> Proxy x' x () a m ()
 each = F.foldr (\a p -> yield a >> p) (return ())
 {-# INLINABLE each #-}
 {-  The above code is the same as:
@@ -647,8 +653,13 @@
     build/foldr fusion
 -}
 
--- | Convert an 'Enumerable' to a 'Producer'
-every :: (Monad m, Enumerable t) => t m a -> Producer' a m ()
+{-| Convert an 'Enumerable' to a 'Producer'
+
+@
+'each' :: ('Monad' m, 'Enumerable' t) => t m a -> 'Producer' a m ()
+@
+-}
+every :: (Monad m, Enumerable t) => t m a -> Proxy x' x () a m ()
 every it = discard >\\ enumerate (toListT it)
 {-# INLINABLE every #-}
 
diff --git a/src/Pipes/Prelude.hs b/src/Pipes/Prelude.hs
--- a/src/Pipes/Prelude.hs
+++ b/src/Pipes/Prelude.hs
@@ -184,8 +184,12 @@
 {-| Read 'String's from a 'IO.Handle' using 'IO.hGetLine'
 
     Terminates on end of input
+
+@
+'fromHandle' :: 'MonadIO' m => 'IO.Handle' -> 'Producer' 'String' m ()
+@
 -}
-fromHandle :: MonadIO m => IO.Handle -> Producer' String m ()
+fromHandle :: MonadIO m => IO.Handle -> Proxy x' x () String m ()
 fromHandle h = go
   where
     go = do
@@ -196,8 +200,11 @@
             go
 {-# INLINABLE fromHandle #-}
 
--- | Repeat a monadic action indefinitely, 'yield'ing each result
-repeatM :: Monad m => m a -> Producer' a m r
+{-| Repeat a monadic action indefinitely, 'yield'ing each result
+
+'repeatM' :: 'Monad' m => m a -> 'Producer' a m r
+-}
+repeatM :: Monad m => m a -> Proxy x' x () a m r
 repeatM m = lift m >~ cat
 {-# INLINABLE [1] repeatM #-}
 
@@ -210,8 +217,12 @@
 > replicateM  0      x = return ()
 >
 > replicateM (m + n) x = replicateM m x >> replicateM n x  -- 0 <= {m,n}
+
+@
+'replicateM' :: 'Monad' m => Int -> m a -> 'Producer' a m ()
+@
 -}
-replicateM :: Monad m => Int -> m a -> Producer' a m ()
+replicateM :: Monad m => Int -> m a -> Proxy x' x () a m ()
 replicateM n m = lift m >~ take n
 {-# INLINABLE replicateM #-}
 
@@ -914,9 +925,9 @@
 
 -- | Zip two 'Producer's
 zip :: Monad m
-    => (Producer   a     m r)
-    -> (Producer      b  m r)
-    -> (Producer' (a, b) m r)
+    => (Producer       a     m r)
+    -> (Producer          b  m r)
+    -> (Proxy x' x () (a, b) m r)
 zip = zipWith (,)
 {-# INLINABLE zip #-}
 
@@ -925,7 +936,7 @@
     => (a -> b -> c)
     -> (Producer  a m r)
     -> (Producer  b m r)
-    -> (Producer' c m r)
+    -> (Proxy x' x () c m r)
 zipWith f = go
   where
     go p1 p2 = do