diff --git a/Debug/SimpleReflect/Expr.hs b/Debug/SimpleReflect/Expr.hs
--- a/Debug/SimpleReflect/Expr.hs
+++ b/Debug/SimpleReflect/Expr.hs
@@ -21,6 +21,7 @@
     ) where
 
 import Data.List
+import Data.Monoid
 import Control.Applicative
 
 ------------------------------------------------------------------------------
@@ -206,3 +207,12 @@
 instance Bounded Expr where
     minBound = var "minBound"
     maxBound = var "maxBound"
+
+------------------------------------------------------------------------------
+-- Other classes
+------------------------------------------------------------------------------
+
+instance Monoid Expr where
+    mempty = var "mempty"
+    mappend = withReduce2 $ op InfixR 6 " <> "
+
diff --git a/simple-reflect.cabal b/simple-reflect.cabal
--- a/simple-reflect.cabal
+++ b/simple-reflect.cabal
@@ -1,12 +1,13 @@
 name:                simple-reflect
-version:             0.2
+version:             0.3
 homepage:            http://twan.home.fmf.nl/blog/haskell/simple-reflection-of-expressions.details
 license:             BSD3
 license-file:        LICENSE
 author:              Twan van Laarhoven
 maintainer:          twanvl@gmail.com
+bug-reports:         https://github.com/twanvl/multiset/issues
 category:            Debug
-cabal-version:       >= 1.2
+cabal-version:       >= 1.6
 build-type:          Simple
 synopsis:            Simple reflection of expressions containing variables
 description:
@@ -15,8 +16,14 @@
     
     The primary aim of this package is teaching and understanding;
     there are no options for manipulating the reflected expressions beyond showing them.
-build-depends:       base
-exposed-modules:
-    Debug.SimpleReflect
-    Debug.SimpleReflect.Expr
-    Debug.SimpleReflect.Vars
+
+source-repository head
+    type:     git
+    location: http://github.com/twanvl/multiset.git
+
+Library
+    build-depends:       base >= 2 && < 5
+    exposed-modules:
+        Debug.SimpleReflect
+        Debug.SimpleReflect.Expr
+        Debug.SimpleReflect.Vars