diff --git a/exact-pi.cabal b/exact-pi.cabal
--- a/exact-pi.cabal
+++ b/exact-pi.cabal
@@ -2,7 +2,7 @@
 -- documentation, see http://haskell.org/cabal/users-guide/
 
 name:                exact-pi
-version:             0.1.1.0
+version:             0.1.2.0
 synopsis:            Exact rational multiples of pi (and integer powers of pi)
 description:         Provides an exact representation for rational multiples of pi alongside an approximate representation of all reals.
                      Useful for storing and computing with conversion factors between physical units.
@@ -21,7 +21,7 @@
   exposed-modules:     Data.ExactPi
   -- other-modules:       
   -- other-extensions:    
-  build-depends:       base >=4.8 && <4.9,
+  build-depends:       base >=4.7 && <4.9,
                        groups >= 0.4 && < 0.5
   hs-source-dirs:      src
   default-language:    Haskell2010
diff --git a/src/Data/ExactPi.hs b/src/Data/ExactPi.hs
--- a/src/Data/ExactPi.hs
+++ b/src/Data/ExactPi.hs
@@ -24,7 +24,9 @@
 )
 where
 
+import Data.Monoid
 import Data.Group
+import Prelude
 
 -- | Represents an exact or approximate real value.
 -- The exactly representable values are rational multiples of an integer power of pi.