diff --git a/Numeric/NumType.lhs b/Numeric/NumType.lhs
--- a/Numeric/NumType.lhs
+++ b/Numeric/NumType.lhs
@@ -300,15 +300,18 @@
 
 > instance ( NegTypeI n, NegTypeI n'
 >          , Negate n p, Negate n' p'
->          , Div (Pos p) (Pos p') (Pos p''))
+>          , Div (Pos p) (Pos p') (Pos p'')
+>          , PosTypeI p'')
 >       => Div (Neg n) (Neg n') (Pos p'')
 > instance ( NegTypeI n, Negate n p'
 >          , Div (Pos p) (Pos p') (Pos p'')
->          , Negate (Pos p'') (Neg n''))
+>          , Negate (Pos p'') (Neg n'')
+>          , PosTypeI p)
 >       => Div (Pos p) (Neg n) (Neg n'')
 > instance ( NegTypeI n, Negate n p'
 >          , Div (Pos p') (Pos p) (Pos p'')
->          , Negate (Pos p'') (Neg n''))
+>          , Negate (Pos p'') (Neg n'')
+>          , PosTypeI p)
 >       => Div (Neg n) (Pos p) (Neg n'')
 
 
@@ -326,8 +329,8 @@
 the 'Div' class having the functional dependency "c b -> a".
 
 > instance (NumTypeI n) => Mul n Zero Zero
-> instance (PosTypeI p, Div c (Pos p) a) => Mul a (Pos p) c
-> instance (NegTypeI n, Div c (Neg n) a) => Mul a (Neg n) c
+> instance (NumTypeI a, NumTypeI c, PosTypeI p, Div c (Pos p) a) => Mul a (Pos p) c
+> instance (NumTypeI a, NumTypeI c, NegTypeI n, Div c (Neg n) a) => Mul a (Neg n) c
 
 
 = Functions =
diff --git a/README b/README
--- a/README
+++ b/README
@@ -1,10 +1,3 @@
 For documentation see the literate haskell source code.
 
-For project information (issues, updates, wiki, examples) see:
-    http://code.google.com/p/dimensional/
-
-To install (requires GHC 6.6 or later):
-    runhaskell Setup.lhs configure
-    runhaskell Setup.lhs build
-    runhaskell Setup.lhs install
-
+If you don't need this particular variation of the library I recommend using numtype-dk (https://github.com/bjornbm/numtype-dk) instead.
diff --git a/changelog.md b/changelog.md
--- a/changelog.md
+++ b/changelog.md
@@ -1,3 +1,13 @@
+1.2 (2016-05-10)
+----------------
+GHC 8.0.1 compatibility fix.
+
+*  Added superclass constraints to `Div` and `Mul` instances.
+
+I don't expect this to break any existing code but am updating
+the major version number just in case. Thanks to Ben Gamari for the patch.
+
+
 1.1 (2014-02)
 -------------
 GHC 7.8.1 compatibility fix.
diff --git a/numtype.cabal b/numtype.cabal
--- a/numtype.cabal
+++ b/numtype.cabal
@@ -1,8 +1,8 @@
 Name:                numtype
-Version:             1.1
+Version:             1.2
 License:             BSD3
 License-File:        LICENSE
-Copyright:           Bjorn Buckwalter 2009-2014
+Copyright:           Bjorn Buckwalter 2009-2016
 Author:              Bjorn Buckwalter
 Maintainer:          bjorn@buckwalter.se
 Stability:           stable
@@ -18,7 +18,6 @@
     integers beyond (-20, 20) this package probably isn't for you.
     It is, however, eminently suitable for applications such as
     representing physical dimensions (see the 'Dimensional' library).
-    Requires GHC 6.6.1 or later.
 Category:            Math
 Build-Type:          Simple
 Build-Depends:       base < 5