diff --git a/src/Data/Basis.hs b/src/Data/Basis.hs
--- a/src/Data/Basis.hs
+++ b/src/Data/Basis.hs
@@ -1,3 +1,7 @@
+-- WARNING: this module depends on type families working fairly well, and
+-- requires ghc version at least 6.9.  I didn't find a way to specify that
+-- dependency in the .cabal.
+-- 
 {-# LANGUAGE TypeOperators, TypeFamilies, UndecidableInstances
   , FlexibleInstances, MultiParamTypeClasses
   #-}
diff --git a/src/Data/Maclaurin.hs b/src/Data/Maclaurin.hs
--- a/src/Data/Maclaurin.hs
+++ b/src/Data/Maclaurin.hs
@@ -1,7 +1,15 @@
 {-# LANGUAGE TypeOperators, MultiParamTypeClasses, UndecidableInstances
            , TypeSynonymInstances, FlexibleInstances, FunctionalDependencies
            , FlexibleContexts
+           , ScopedTypeVariables
   #-}
+
+-- The ScopedTypeVariables is there just as a bug work-around.  Without it
+-- I get a bogus error about context mismatch for mutually recursive
+-- definitions.  This bug was introduced between ghc 6.9.20080622 and
+-- 6.10.0.20081007.
+
+
 -- {-# OPTIONS_GHC -ddump-simpl-stats -ddump-simpl #-}
 
 -- TODO: remove FlexibleContexts
diff --git a/vector-space.cabal b/vector-space.cabal
--- a/vector-space.cabal
+++ b/vector-space.cabal
@@ -1,7 +1,7 @@
 Name:                vector-space
-Version:             0.3
+Version:             0.3.1
 Cabal-Version:       >= 1.2
-Synopsis:            Vector & affine spaces, linear maps, and derivatives
+Synopsis:            Vector & affine spaces, linear maps, and derivatives (requires ghc 6.9)
 Category:            math
 Description:
   '''vector-space''' provides classes and generic operations for vector
@@ -28,6 +28,9 @@
 Stability:           experimental
 build-type:          Simple
 
+-- WARNING: Data.Basis depends on type families working fairly well,
+-- and requires ghc version at least 6.9.  I don't know how to specify
+-- that dependency in the .cabal.
 
 Library
   hs-Source-Dirs:      src