diff --git a/lub.cabal b/lub.cabal
--- a/lub.cabal
+++ b/lub.cabal
@@ -1,5 +1,5 @@
 Name:                lub
-Version:             0.0.5
+Version:             0.0.6
 Cabal-Version:       >= 1.2
 Synopsis:            least upper bounds -- information merging
 Category:            Concurrency, Data, Other
@@ -17,7 +17,7 @@
 Author:              Conal Elliott 
 Maintainer:          conal@conal.net
 Homepage:            http://haskell.org/haskellwiki/lub
-Package-Url:         http://code.haskell.org/lub
+Package-Url:         http://code.haskell.org/~conal/code/lub
 Copyright:           (c) 2008 by Conal Elliott
 License:             BSD3
 Stability:           experimental
@@ -26,7 +26,7 @@
 Library
   hs-Source-Dirs:      src
   Extensions:
-  Build-Depends:       base, unamb >= 0.1.3
+  Build-Depends:       base < 5, unamb >= 0.1.3
   Exposed-Modules:     
                        Data.Repr
                        Data.Lub
diff --git a/src/Data/Lub.hs b/src/Data/Lub.hs
--- a/src/Data/Lub.hs
+++ b/src/Data/Lub.hs
@@ -27,7 +27,7 @@
 import Control.Applicative (liftA2)
 
 import Data.Unamb hiding (parCommute)
-import qualified Data.Unamb as Unamb
+-- import qualified Data.Unamb as Unamb
 
 import Data.Repr
 
@@ -143,7 +143,7 @@
 -- parallel, 'lub'-merging the results.  Useful when there are special
 -- cases that don't require evaluating both arguments.
 -- 
--- Similar to 'Unamb.parCommute', but uses 'lub' instead of 'unamb'.
+-- Similar to parCommute from Unamb, but uses 'lub' instead of 'unamb'.
 parCommute :: HasLub b => (a -> a -> b) -> (a -> a -> b)
 parCommute op x y = (x `op` y) `lub` (y `op` x)
 
@@ -173,5 +173,18 @@
 0     *    undefined :: Integer
 0 `ptimes` undefined :: Integer
 undefined `ptimes` 0 :: Integer
+
+zip' :: (HasLub a, HasLub b) => [a] -> [b] -> [(a,b)]
+zip' = lubs [p1,p2,p3]
+ where
+   p1 []     _      = []
+   p2 _      []     = []
+   p3 (x:xs) (y:ys) = (x,y) : zip' xs ys
+
+zip' [] (error "boom") :: [(Int,Int)]
+zip' (error "boom") [] :: [(Int,Int)]
+
+zip' [10,20] (1 : 2 : error "boom")
+zip' (1 : 2 : error "boom") [10,20]
 
 -}