diff --git a/datadog-tracing.cabal b/datadog-tracing.cabal
--- a/datadog-tracing.cabal
+++ b/datadog-tracing.cabal
@@ -1,6 +1,6 @@
 cabal-version:       2.2
 name:                datadog-tracing
-version:             1.3.2
+version:             1.3.3
 synopsis:            Datadog tracing client and mock agent.
 license:             BSD-3-Clause
 license-file:        LICENSE
@@ -69,7 +69,9 @@
   hs-source-dirs:     exe
   main-is:            Main.hs
   build-depends:    , datadog-tracing
+                    , data-default         ^>= 0.7.1.1
                     , servant-server       ^>= 0.14.1
+                    , wai-extra            ^>= 3.0.25
                     , warp                 ^>= 3.2.25
   ghc-options:        -threaded
 
diff --git a/exe/Main.hs b/exe/Main.hs
--- a/exe/Main.hs
+++ b/exe/Main.hs
@@ -9,10 +9,13 @@
 -- exposed that allows downloading all the recorded data in a format compatible
 -- with Jaeger tracing.
 
-import           Control.Monad.IO.Class   (liftIO)
+import           Control.Monad.IO.Class                    (liftIO)
+import           Data.Default                              (def)
 import           Data.IORef
-import qualified Data.Map.Strict          as M
-import           Network.Wai.Handler.Warp (run)
+import qualified Data.Map.Strict                           as M
+import           Network.Wai.Handler.Warp                  (run)
+import           Network.Wai.Middleware.RequestLogger
+import           Network.Wai.Middleware.RequestLogger.JSON (formatAsJSON)
 import           Servant
 
 import           Datadog.Agent
@@ -23,8 +26,12 @@
 main :: IO ()
 main = do
   ref <- newIORef []
+  logger <- mkRequestLogger $ def {
+      outputFormat = CustomOutputFormatWithDetails formatAsJSON
+    }
+
   let services = (postTraces3 ref) :<|> (postTraces4 ref) :<|> (getTraces ref)
-  run 8126 (serve (Proxy @ Services) services)
+  run 8126 (logger $ serve (Proxy @ Services) services)
 
 postTraces3 :: IORef [Trace] -> [Trace] -> Handler NoContent
 postTraces3 r t = (\_ -> NoContent) <$> postTraces4 r t
diff --git a/library/Data/MessagePack/Aeson.hs b/library/Data/MessagePack/Aeson.hs
--- a/library/Data/MessagePack/Aeson.hs
+++ b/library/Data/MessagePack/Aeson.hs
@@ -2,7 +2,9 @@
 --   http://hackage.haskell.org/package/msgpack-aeson-0.1.0.0/docs/src/Data-MessagePack-Aeson.html#toAeson
 --   with only minor changes to use the data-msgpack fork (mostly changing Vector to list).
 
-{-# LANGUAGE LambdaCase #-}
+{-# LANGUAGE LambdaCase          #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE TypeApplications    #-}
 
 -- | Aeson bridge for MessagePack
 --
@@ -17,12 +19,15 @@
 import           Data.Scientific
 import qualified Data.Text.Encoding   as T
 import qualified Data.Vector          as V
+import           Data.Word            (Word64)
 
 toAeson :: MP.Object -> A.Result Value
 toAeson = \case
   ObjectNil      -> pure Null
   ObjectBool b   -> pure . Bool $ b
-  ObjectInt n    -> pure . Number $ fromIntegral n
+  ObjectInt n    ->
+    let w64 :: Word64 = fromIntegral n -- WARNING: silent wraparound biased to unsigned integers, fixed in next msgpack
+    in  pure . Number . fromIntegral $ w64
   ObjectFloat f  -> pure . Number $ realToFrac f
   ObjectDouble d -> pure . Number $ realToFrac d
   ObjectStr t    -> pure . String $ t
@@ -39,9 +44,9 @@
   Null        -> ObjectNil
   Bool b      -> ObjectBool b
   Number s ->
-    case floatingOrInteger s of
+    case floatingOrInteger @Double @Integer s of
       Left f  -> ObjectDouble f
-      Right n -> ObjectInt n
+      Right n -> ObjectInt (fromInteger n) -- WARNING: silent wraparound, fixed in next msgpack
   String t    -> ObjectStr t
   Array v     -> ObjectArray $ V.map fromAeson v
   A.Object o  -> ObjectMap $ V.fromList $ map (toObject *** fromAeson) $ HM.toList o
diff --git a/library/Datadog/Jaeger.hs b/library/Datadog/Jaeger.hs
--- a/library/Datadog/Jaeger.hs
+++ b/library/Datadog/Jaeger.hs
@@ -38,10 +38,11 @@
             (M.fromList $ (\a -> (ProcessID a, Process a)) <$> services spans)
     spanToSpan Agent.Span{..} =
       let traceId = (TraceID . showt $ spanTraceId)
-      in Span (SpanID . showt $ spanId)
+          mkSpan s = SpanID $ (showt spanTraceId) <> "-" <> (showt s)
+      in Span (mkSpan spanId)
               traceId
               (Name spanName)
-              ((Reference traceId) . (SpanID . showt) <$> maybeToList spanParentId)
+              ((Reference traceId) . mkSpan <$> maybeToList spanParentId)
               (toInteger spanStart)
               (toInteger spanDuration)
               (mkTag <$> (concat $ M.toList <$> spanMeta))