diff --git a/musicw.cabal b/musicw.cabal
--- a/musicw.cabal
+++ b/musicw.cabal
@@ -1,5 +1,5 @@
 name:                musicw
-version:             0.3.7
+version:             0.3.8
 synopsis:            Sound synthesis library, to be used with GHCJS and Web Audio API
 description:         A library for sound synthesis, currently targeting GHCJS and the Web Audio API. Used by Inner Ear, Estuary, Punctual and possibly other projects.
 homepage:            https://github.com/dktr0/musicw/blob/master/README.md
diff --git a/src/Sound/MusicW/Node.hs b/src/Sound/MusicW/Node.hs
--- a/src/Sound/MusicW/Node.hs
+++ b/src/Sound/MusicW/Node.hs
@@ -300,7 +300,7 @@
 disconnectNodes :: MonadIO m => Node -> Node -> m ()
 disconnectNodes from to
   | not (js_isSource from) = error $ (show from) ++ " can't be disconnect source."
-  | not (js_isSink to) == False = error $ (show to) ++ " can't be disconnect target."
+  | not (js_isSink to) = error $ (show to) ++ " can't be disconnect target."
   | otherwise   = liftIO $ js_disconnect from to
 
 disconnectAll :: MonadIO m => Node -> m ()