diff --git a/main/Act.hs b/main/Act.hs
--- a/main/Act.hs
+++ b/main/Act.hs
@@ -1,4 +1,5 @@
 {-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE FlexibleContexts    #-}
 module Act
   ( main
   ) where
@@ -74,16 +75,19 @@
 encodeText :: ToJSON a => a -> Text
 encodeText = toStrict . toLazyText . encodeToTextBuilder . toJSON
 
-exec :: MonadIO m => Args -> Container -> Uid -> Metadata -> [Blob] -> m (Metadata, [Artifact])
+handler :: MonadBaseControl IO m => m () -> m (Maybe SomeException)
+handler a = handle (return . Just) $ a >> return Nothing
+
+exec :: MonadIO m => Args -> Container -> Uid -> Metadata -> [Blob] -> m (Metadata, [Artifact], Maybe SomeException)
 exec Args{..} container uid metadata blobs =
   shelly $ withDir $ \dir dataDir storeDir -> do
     control $ dataDir </> pack "control.json"
     storeInput $ storeDir </> pack "input"
     dataInput $ dataDir </> pack "input.json"
-    maybe (docker dataDir storeDir container) (bash dir container) aContainerless
+    e <- maybe (docker dataDir storeDir container) (bash dir container) aContainerless
     result <- dataOutput $ dataDir </> pack "output.json"
     artifacts <- storeOutput $ storeDir </> pack "output"
-    return (result, artifacts) where
+    return (result, artifacts, e) where
       withDir action =
         withTmpDir $ \dir -> do
           mkdir $ dir </> pack "data"
@@ -129,25 +133,27 @@
       storeOutput dir = do
         artifacts <- findWhen test_f dir
         forM artifacts $ readArtifact dir
-      docker dataDir storeDir Container{..} = do
-        devices <- forM cDevices $ \device ->
-          liftM strip $ run "readlink" ["-f", device]
-        run_ "docker" $ concat
-          [["run"]
-          , concatMap (("--device" :)  . return) devices
-          , concatMap (("--env"    :)  . return) cEnvironment
-          , concatMap (("--link"    :) . return) cLink
-          , concatMap (("--volume" :)  . return) $
-              toTextIgnore dataDir  <> ":/app/data"  :
-              toTextIgnore storeDir <> ":/app/store" : cVolumes
-          , [cImage]
-          , words cCommand
-          ]
-      bash dir Container{..} bashDir = do
-        files <- ls $ fromText $ pack bashDir
-        forM_ files $ flip cp_r dir
-        cd dir
-        maybe (return ()) (uncurry $ run_ . fromText) $ uncons $ words cCommand
+      docker dataDir storeDir Container{..} =
+        handler $ do
+          devices <- forM cDevices $ \device ->
+            liftM strip $ run "readlink" ["-f", device]
+          run_ "docker" $ concat
+            [["run"]
+            , concatMap (("--device" :)  . return) devices
+            , concatMap (("--env"    :)  . return) cEnvironment
+            , concatMap (("--link"    :) . return) cLink
+            , concatMap (("--volume" :)  . return) $
+                toTextIgnore dataDir  <> ":/app/data"  :
+                toTextIgnore storeDir <> ":/app/store" : cVolumes
+            , [cImage]
+            , words cCommand
+            ]
+      bash dir Container{..} bashDir =
+        handler $ do
+          files <- ls $ fromText $ pack bashDir
+          forM_ files $ flip cp_r dir
+          cd dir
+          maybe (return ()) (uncurry $ run_ . fromText) $ uncons $ words cCommand
 
 call :: Args -> IO ()
 call Args{..} = do
diff --git a/main/Act2.hs b/main/Act2.hs
--- a/main/Act2.hs
+++ b/main/Act2.hs
@@ -1,4 +1,5 @@
 {-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE FlexibleContexts    #-}
 module Act2
   ( main
   ) where
@@ -50,16 +51,19 @@
 encodeText :: ToJSON a => a -> Text
 encodeText = toStrict . toLazyText . encodeToTextBuilder . toJSON
 
-exec :: MonadIO m => Text -> Uid -> Metadata -> [Blob] -> m (Metadata, [Artifact])
+handler :: MonadBaseControl IO m => m () -> m (Maybe SomeException)
+handler a = handle (return . Just) $ a >> return Nothing
+
+exec :: MonadIO m => Text -> Uid -> Metadata -> [Blob] -> m (Metadata, [Artifact], Maybe SomeException)
 exec cmdline uid metadata blobs =
   shelly $ withDir $ \dir dataDir storeDir -> do
     control $ dataDir </> pack "control.json"
     storeInput $ storeDir </> pack "input"
     dataInput $ dataDir </> pack "input.json"
-    bash dir
+    e <- bash dir
     result <- dataOutput $ dataDir </> pack "output.json"
     artifacts <- storeOutput $ storeDir </> pack "output"
-    return (result, artifacts) where
+    return (result, artifacts, e) where
       withDir action =
         withTmpDir $ \dir -> do
           mkdir $ dir </> pack "data"
@@ -93,12 +97,13 @@
       storeOutput dir = do
         artifacts <- findWhen test_f dir
         forM artifacts $ readArtifact dir
-      bash dir = do
-        bashDir <- pwd
-        files <- ls bashDir
-        forM_ files $ flip cp_r dir
-        cd dir
-        maybe (return ()) (uncurry $ run_ . fromText) $ uncons $ words cmdline
+      bash dir =
+        handler $ do
+          bashDir <- pwd
+          files <- ls bashDir
+          forM_ files $ flip cp_r dir
+          cd dir
+          maybe (return ()) (uncurry $ run_ . fromText) $ uncons $ words cmdline
 
 call :: Args -> IO ()
 call Args{..} = do
diff --git a/src/Network/AWS/Flow.hs b/src/Network/AWS/Flow.hs
--- a/src/Network/AWS/Flow.hs
+++ b/src/Network/AWS/Flow.hs
@@ -36,7 +36,6 @@
 import           Data.Char
 import qualified Data.HashMap.Strict as Map
 import           Data.Text ( pack )
-import           Data.Typeable
 import           Formatting hiding ( string )
 import           Network.AWS.SWF
 import           Network.HTTP.Types
@@ -94,13 +93,12 @@
 
 actException :: MonadFlow m => Token -> SomeException -> m ()
 actException token e = do
-  logError' $ sformat ("event=act-exception-type " % stext) $ show $ typeOf e
   logError' $ sformat ("event=act-exception " % stext) $ show e
   maybe' ((textToString $ show e) =~ exitCode) (respondActivityTaskFailedAction token) $ \code -> do
     if code == 255 then respondActivityTaskCanceledAction token else
       respondActivityTaskFailedAction token
 
-act :: MonadFlow m => Queue -> (Uid -> Metadata -> [Blob] -> m (Metadata, [Artifact])) -> m ()
+act :: MonadFlow m => Queue -> (Uid -> Metadata -> [Blob] -> m (Metadata, [Artifact], Maybe SomeException)) -> m ()
 act queue action =
   handle serializeError $ do
     logInfo' "event=act"
@@ -112,13 +110,12 @@
     unless (null keys) $ logInfo' $ sformat ("event=list-blobs uid=" % stext) uid
     blobs <- forM keys $ getObjectAction uid
     unless (null blobs) $ logInfo' $ sformat ("event=blobs uid=" % stext) uid
-    handle (actException token) $ do
-      (output, artifacts) <- action uid input blobs
-      maybe_ output $ logDebug' . sformat ("event=act-output " % stext)
-      logInfo' $ sformat ("event=act-finish uid=" % stext) uid
-      forM_ artifacts $ putObjectAction uid
-      unless (null artifacts) $ logInfo' $ sformat ("event=artifacts uid=" % stext) uid
-      respondActivityTaskCompletedAction token output
+    (output, artifacts, e) <- action uid input blobs
+    maybe_ output $ logDebug' . sformat ("event=act-output " % stext)
+    logInfo' $ sformat ("event=act-finish uid=" % stext) uid
+    forM_ artifacts $ putObjectAction uid
+    unless (null artifacts) $ logInfo' $ sformat ("event=artifacts uid=" % stext) uid
+    maybe (respondActivityTaskCompletedAction token output) (actException token) e
 
 decide :: MonadFlow m => Plan -> m ()
 decide plan@Plan{..} =
diff --git a/wolf.cabal b/wolf.cabal
--- a/wolf.cabal
+++ b/wolf.cabal
@@ -1,5 +1,5 @@
 name:                wolf
-version:             0.2.7
+version:             0.2.8
 synopsis:            Amazon Simple Workflow Service Wrapper.
 homepage:            https://github.com/swift-nav/wolf
 license:             MIT