diff --git a/src/Servant/Client/Core/Internal/HasClient.hs b/src/Servant/Client/Core/Internal/HasClient.hs
index 712007006..6be92ec6d 100644
--- a/src/Servant/Client/Core/Internal/HasClient.hs
+++ b/src/Servant/Client/Core/Internal/HasClient.hs
@@ -16,6 +16,8 @@ module Servant.Client.Core.Internal.HasClient where
 import           Prelude ()
 import           Prelude.Compat
 
+import           Control.Concurrent.MVar
+                 (modifyMVar, newMVar)
 import qualified Data.ByteString                        as BS
 import qualified Data.ByteString.Lazy                   as BL
 import           Data.Foldable
@@ -36,13 +38,14 @@ import qualified Network.HTTP.Types                     as H
 import           Servant.API
                  ((:<|>) ((:<|>)), (:>), AuthProtect, BasicAuth, BasicAuthData,
                  BuildHeadersTo (..), Capture', CaptureAll, Description,
-                 EmptyAPI, FramingUnrender (..), FromSourceIO (..), Header',
-                 Headers (..), HttpVersion, IsSecure, MimeRender (mimeRender),
+                 EmptyAPI, FramingRender (..), FramingUnrender (..),
+                 FromSourceIO (..), Header', Headers (..), HttpVersion,
+                 IsSecure, MimeRender (mimeRender),
                  MimeUnrender (mimeUnrender), NoContent (NoContent), QueryFlag,
                  QueryParam', QueryParams, Raw, ReflectMethod (..), RemoteHost,
                  ReqBody', SBoolI, Stream, StreamBody', Summary, ToHttpApiData,
-                 Vault, Verb, WithNamedContext, contentType, getHeadersHList,
-                 getResponse, toQueryParam, toUrlPiece)
+                 ToSourceIO (..), Vault, Verb, WithNamedContext, contentType,
+                 getHeadersHList, getResponse, toQueryParam, toUrlPiece)
 import           Servant.API.ContentTypes
                  (contentTypes)
 import           Servant.API.Modifiers
@@ -538,7 +541,7 @@ instance (MimeRender ct a, HasClient m api)
     hoistClientMonad pm (Proxy :: Proxy api) f (cl a)
 
 instance
-    ( HasClient m api
+    ( HasClient m api, MimeRender ctype chunk, FramingRender framing, ToSourceIO chunk a
     ) => HasClient m (StreamBody' mods framing ctype a :> api)
   where
 
@@ -547,7 +550,39 @@ instance
     hoistClientMonad pm _ f cl = \a ->
       hoistClientMonad pm (Proxy :: Proxy api) f (cl a)
 
-    clientWithRoute _pm Proxy _req _body = error "HasClient @StreamBody"
+    clientWithRoute pm Proxy req body
+        = clientWithRoute pm (Proxy :: Proxy api)
+        $ setRequestBody (RequestBodyStreamChunked givesPopper) (contentType ctypeP) req
+      where
+        ctypeP   = Proxy :: Proxy ctype
+        framingP = Proxy :: Proxy framing
+
+        sourceIO = framingRender
+            framingP
+            (mimeRender ctypeP :: chunk -> BL.ByteString)
+            (toSourceIO body)
+
+        -- not pretty.
+        givesPopper :: (IO BS.ByteString -> IO ()) -> IO ()
+        givesPopper needsPopper = S.unSourceT sourceIO $ \step0 -> do
+            ref <- newMVar step0
+
+            -- Note sure we need locking, but it's feels safer.
+            let popper :: IO BS.ByteString
+                popper = modifyMVar ref nextBs
+
+            needsPopper popper
+
+        nextBs S.Stop          = return (S.Stop, BS.empty)
+        nextBs (S.Error err)   = fail err
+        nextBs (S.Skip s)      = nextBs s
+        nextBs (S.Effect ms)   = ms >>= nextBs
+        nextBs (S.Yield lbs s) = case BL.toChunks lbs of
+            []     -> nextBs s
+            (x:xs) | BS.null x -> nextBs step'
+                   | otherwise -> return (step', x)
+                where
+                  step' = S.Yield (BL.fromChunks xs) s