diff --git a/bearriver.cabal b/bearriver.cabal
--- a/bearriver.cabal
+++ b/bearriver.cabal
@@ -1,5 +1,5 @@
 name:                bearriver
-version:             0.10.4.5
+version:             0.10.4.6
 synopsis:            A replacement of Yampa based on Monadic Stream Functions.
 description:         A Yampa replacement built using Dunai.
 homepage:            keera.co.uk
diff --git a/src/FRP/BearRiver.hs b/src/FRP/BearRiver.hs
--- a/src/FRP/BearRiver.hs
+++ b/src/FRP/BearRiver.hs
@@ -1,4 +1,5 @@
 {-# LANGUAGE Arrows     #-}
+{-# LANGUAGE CPP        #-}
 {-# LANGUAGE RankNTypes #-}
 module FRP.BearRiver
   (module FRP.BearRiver, module X)
@@ -227,7 +228,11 @@
   let b'' = event b' (f b') a
   in (b'', b'')
 
+#if MIN_VERSION_base(4,8,0)
 parB :: (Monad m) => [SF m a b] -> SF m a [b]
+#else
+parB :: (Functor m, Monad m) => [SF m a b] -> SF m a [b]
+#endif
 parB = widthFirst . sequenceS
 
 dpSwitchB :: (Monad m , Traversable col)