diff --git a/src/Network/Warped/Application.hs b/src/Network/Warped/Application.hs
--- a/src/Network/Warped/Application.hs
+++ b/src/Network/Warped/Application.hs
@@ -18,12 +18,14 @@
   , answer
   , answerStatus
   , answerSource
+  , answerJson
   , withHeader
   ) where
 
 import Blaze.ByteString.Builder
 import Control.Concurrent.Async.Lifted
 import Control.Monad.Trans.Control
+import Data.Aeson
 import Data.Conduit
 import Data.UUID                       hiding (fromByteString)
 import Network.HTTP.Types
@@ -107,7 +109,7 @@
 answerStatus :: MonadWai c m => Status -> ResponseHeaders -> m ResponseReceived
 answerStatus status headers = do
   sessionUid <- view wcSessionUid
-  let headers' = (hSessionUid, toASCIIBytes sessionUid) : headers
+  let headers' = hSessionUid =. toASCIIBytes sessionUid : headers
   answer $ responseLBS status headers' mempty
 
 -- | Stream response.
@@ -115,8 +117,16 @@
 answerSource :: MonadWai c m => Status -> ResponseHeaders -> Source IO (Flush Builder) -> m ResponseReceived
 answerSource status headers response = do
   sessionUid <- view wcSessionUid
-  let headers' = (hSessionUid, toASCIIBytes sessionUid) : headers
+  let headers' = hSessionUid =. toASCIIBytes sessionUid : headers
   answer $ responseSource status headers' response
+
+-- | JSON response.
+--
+answerJson :: (MonadWai c m, ToJSON a) => Status -> ResponseHeaders -> a -> m ResponseReceived
+answerJson status headers value = do
+  sessionUid <- view wcSessionUid
+  let headers' = hSessionUid =. toASCIIBytes sessionUid : headers
+  answer $ responseLBS status headers' $ encode value
 
 -- | Lookup header.
 --
diff --git a/warped.cabal b/warped.cabal
--- a/warped.cabal
+++ b/warped.cabal
@@ -1,5 +1,5 @@
 name:                  warped
-version:               0.0.2
+version:               0.0.3
 synopsis:              Warp and Wai Library.
 description:           Library support around WAI and warp server.
 homepage:              https://github.com/swift-nav/warped
@@ -27,7 +27,8 @@
                      , Network.Warped.Types.Ctx
   ghc-options:         -Wall
   default-language:    Haskell2010
-  build-depends:       base >= 4.9 && < 5
+  build-depends:       aeson
+                     , base >= 4.9 && < 5
                      , blaze-builder
                      , conduit
                      , http-types