diff --git a/colorless-scotty.cabal b/colorless-scotty.cabal
--- a/colorless-scotty.cabal
+++ b/colorless-scotty.cabal
@@ -3,7 +3,7 @@
 -- see: https://github.com/sol/hpack
 
 name:           colorless-scotty
-version:        0.0.0
+version:        0.0.1
 synopsis:       Scotty server add-on for Colorless
 description:    Scotty server add-on for Colorless
 category:       Web
diff --git a/library/Colorless/Server/Scotty.hs b/library/Colorless/Server/Scotty.hs
--- a/library/Colorless/Server/Scotty.hs
+++ b/library/Colorless/Server/Scotty.hs
@@ -9,6 +9,7 @@
   ) where
 
 import qualified Network.Wai as Wai
+import qualified Control.Monad.Except as M
 import Web.Scotty.Trans
 import Control.Monad.Trans (lift)
 import Colorless.Server (Pull(..), RuntimeThrower, Request, Response, Version, Major, Minor)
@@ -18,7 +19,7 @@
 type WaiResponse = Wai.Response
 
 runServer
-  :: (MonadIO m, RuntimeThrower m, MonadIO n)
+  :: (MonadIO m, MonadIO n)
   => Pull
   -> (m WaiResponse -> IO WaiResponse)
   -> ScottyT e m ()
@@ -26,9 +27,9 @@
 runServer Pull{port} = scottyT port
 
 sendResponse
-  :: (ScottyError e, MonadIO m, RuntimeThrower m)
+  :: (ScottyError e, MonadIO m)
   => Pull
-  -> Map Major (Minor, Request -> m Response)
+  -> Map Major (Minor, Request -> m (Either Response Response))
   -> ScottyT e m ()
 sendResponse Pull{path} handlerMap = post (literal $ fromText path) $ do
   req <- jsonData
@@ -36,10 +37,10 @@
   json resp
 
 sendResponseSingleton
-  :: (ScottyError e, MonadIO m, RuntimeThrower m)
+  :: (ScottyError e, MonadIO m)
   => Pull
   -> Version
-  -> (Request -> m Response)
+  -> (Request -> m (Either Response Response))
   -> ScottyT e m ()
 sendResponseSingleton Pull{path} version handler = post (literal $ fromText path) $ do
   req <- jsonData
diff --git a/package.yaml b/package.yaml
--- a/package.yaml
+++ b/package.yaml
@@ -1,5 +1,5 @@
 name: colorless-scotty
-version: '0.0.0'
+version: '0.0.1'
 category: Web
 synopsis: Scotty server add-on for Colorless
 description: Scotty server add-on for Colorless