diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,13 @@
 # Changelog
 
+## 0.32
+
+* Add `addHeader` dictionary combinator, to extend instead of replace
+  the header dictionaries. For this, a constructor `TwoHeaders` was
+  added to `Header`.
+* Relax the types of `mkListing` and `mkOrderedListing` to allow
+  parameters and headers.
+
 ### 0.31.1
 
 * Expose `Rest.Driver.Routing.splitUriString`.
diff --git a/rest-core.cabal b/rest-core.cabal
--- a/rest-core.cabal
+++ b/rest-core.cabal
@@ -1,5 +1,5 @@
 name:                rest-core
-version:             0.31.1
+version:             0.32
 description:         Rest API library.
 synopsis:            Rest API library.
 maintainer:          code@silk.co
@@ -39,7 +39,7 @@
     Rest.Schema
   build-depends:
       base >= 4.5 && < 4.8
-    , aeson >= 0.7 && < 0.8
+    , aeson >= 0.7 && < 0.9
     , aeson-utils == 0.2.*
     , bytestring >= 0.9 && < 0.11
     , either >= 3.4 && < 4.4
diff --git a/src/Rest/Dictionary/Combinators.hs b/src/Rest/Dictionary/Combinators.hs
--- a/src/Rest/Dictionary/Combinators.hs
+++ b/src/Rest/Dictionary/Combinators.hs
@@ -39,6 +39,7 @@
   -- ** Header dictionaries
 
   , mkHeader
+  , addHeader
 
   -- ** Parameter dictionaries
 
@@ -61,10 +62,15 @@
 import Rest.Dictionary.Types
 import Rest.Info
 
--- | Add custom sub-dictionary for recognizing headers.
+-- | Set custom sub-dictionary for recognizing headers.
 
 mkHeader :: Header h -> Dict x p i o e -> Dict h p i o e
 mkHeader = L.set headers
+
+-- | Add custom sub-dictionary for recognizing headers.
+
+addHeader :: Header h -> Dict h' p i o e -> Dict (h, h') p i o e
+addHeader = L.modify headers . TwoHeaders
 
 -- | Set custom sub-dictionary for recognizing parameters.
 
diff --git a/src/Rest/Dictionary/Types.hs b/src/Rest/Dictionary/Types.hs
--- a/src/Rest/Dictionary/Types.hs
+++ b/src/Rest/Dictionary/Types.hs
@@ -85,18 +85,20 @@
 -- for generating documentation. The second field is a custom parser that can
 -- fail with a `DataError` or can produce a some value. When explicitly not
 -- interested in the headers we can use `NoHeader`.
---
--- Todo: allow multiple parsers for different headers instead of combining them
--- into one parser + use `Info` class to enfore some documention about the
--- parsed type.
 
 data Header h where
-  NoHeader ::                                                       Header ()
-  Header   :: [String] -> ([Maybe String] -> Either DataError h) -> Header h
+  NoHeader    ::                                                       Header ()
+  Header      :: [String] -> ([Maybe String] -> Either DataError h) -> Header h
+  TwoHeaders  :: Header h -> Header k                               -> Header (h,k)
 
 instance Show (Header h) where
-  showsPrec _ NoHeader      = showString "NoHeader"
-  showsPrec n (Header hs _) = showParen (n > 9) (showString "Header " . showsPrec 10 hs)
+  showsPrec _ NoHeader         = showString "NoHeader"
+  showsPrec n (Header hs _)    = showParen (n > 9) (showString "Header " . showsPrec 10 hs)
+  showsPrec n (TwoHeaders h k) = showParen (n > 9) ( showString "TwoHeaders "
+                                                   . showsPrec 10 h
+                                                   . showString " "
+                                                   . showsPrec 10 k
+                                                   )
 
 -- | The explicit dictionary `Parameter` describes how to translate the request
 -- parameters to some Haskell value. The first field in the `Header`
@@ -104,10 +106,6 @@
 -- validation and for generating documentation. The second field is a custom
 -- parser that can fail with a `DataError` or can produce a some value. When
 -- explicitly not interested in the parameters we can use `NoParam`.
---
--- Todo: allow multiple parsers for different parameters instead of combining
--- them into one parser + use `Info` class to enfore some documention about the
--- parsed type.
 
 data Param p where
   NoParam   ::                                                       Param ()
diff --git a/src/Rest/Driver/Perform.hs b/src/Rest/Driver/Perform.hs
--- a/src/Rest/Driver/Perform.hs
+++ b/src/Rest/Driver/Perform.hs
@@ -190,6 +190,7 @@
 headers :: Rest m => Header h -> ErrorT DataError m h
 headers NoHeader      = return ()
 headers (Header xs h) = mapM getHeader xs >>= either throwError return . h
+headers (TwoHeaders h1 h2) = (,) <$> headers h1 <*> headers h2
 
 parameters :: Rest m => Param p -> ErrorT DataError m p
 parameters NoParam      = return ()
diff --git a/src/Rest/Handler.hs b/src/Rest/Handler.hs
--- a/src/Rest/Handler.hs
+++ b/src/Rest/Handler.hs
@@ -96,10 +96,11 @@
 data Range = Range { offset :: Int, count :: Int }
 
 -- | Smart constructor for creating a list handler.
+-- Restricts the type of the 'Input' dictionary to 'None'
 
 mkListing
   :: Monad m
-  => Modifier () () () o e
+  => Modifier h p () o e
   -> (Range -> ErrorT (Reason e) m [o])
   -> ListHandler m
 mkListing d a = mkGenHandler (mkPar range . d) (a . param)
@@ -122,10 +123,11 @@
                             }
 
 -- | Create a list handler that accepts ordering information.
+-- Restricts the type of the 'Input' dictionary to 'None'
 
 mkOrderedListing
   :: Monad m
-  => Modifier () () () o e
+  => Modifier h p () o e
   -> ((Range, Maybe String, Maybe String) -> ErrorT (Reason e) m [o])
   -> ListHandler m
 mkOrderedListing d a = mkGenHandler (mkPar orderedRange . d) (a . param)