diff --git a/Shakefile.hs b/Shakefile.hs
--- a/Shakefile.hs
+++ b/Shakefile.hs
@@ -21,6 +21,10 @@
         , "src//*.hs"
         ]
 
+  -- | Haskell rules.
+  --
+  hsRules "."
+
   -- | Cabal rules.
   --
   cabalRules "." "preamble.cabal"
diff --git a/preamble.cabal b/preamble.cabal
--- a/preamble.cabal
+++ b/preamble.cabal
@@ -1,5 +1,5 @@
 name:                  preamble
-version:               0.0.19
+version:               0.0.20
 synopsis:              Yet another prelude.
 description:           A prelude built on basic-prelude.
 homepage:              https://github.com/swift-nav/preamble
diff --git a/src/Preamble/Prelude.hs b/src/Preamble/Prelude.hs
--- a/src/Preamble/Prelude.hs
+++ b/src/Preamble/Prelude.hs
@@ -10,7 +10,9 @@
   , either'
   , maybe_
   , eitherThrowIO
+  , eitherThrowIO'
   , maybeThrowIO
+  , maybeThrowIO'
   , boolThrowIO
   , textFromString
   , (-/-)
@@ -40,15 +42,25 @@
 maybe_ :: Monad m => Maybe a -> (a -> m ()) -> m ()
 maybe_ = flip $ maybe $ return ()
 
+-- | Throw Exception on either error.
+--
+eitherThrowIO :: (MonadIO m, Exception e) => Either e a -> m a
+eitherThrowIO = either (liftIO . throwIO) return
+
 -- | Throw userError on either error.
 --
-eitherThrowIO :: MonadIO m => Either String a -> m a
-eitherThrowIO = either (liftIO . throwIO . userError) return
+eitherThrowIO' :: MonadIO m => Either String a -> m a
+eitherThrowIO' = either (liftIO . throwIO . userError) return
 
+-- | Throw Exception on maybe nothing.
+--
+maybeThrowIO :: (MonadIO m, Exception e) => e -> Maybe a -> m a
+maybeThrowIO e = maybe (liftIO $ throwIO e) return
+
 -- | Throw userError on maybe nothing.
 --
-maybeThrowIO :: MonadIO m => String -> Maybe a -> m a
-maybeThrowIO s = maybe (liftIO $ throwIO $ userError s) return
+maybeThrowIO' :: MonadIO m => String -> Maybe a -> m a
+maybeThrowIO' s = maybe (liftIO $ throwIO $ userError s) return
 
 -- | Throw userError on false.
 --