diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,5 +1,9 @@
 # Changelog for S-expresso
 
+Version 1.2.1.0
+---------------
+* Add `Data` instances. [#12](https://github.com/archambaultv/sexpresso/pull/12).
+
 Version 1.2.0.0
 ---------------
 * Update to stack lts 18.10
diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -1,6 +1,10 @@
 [![License OBSD](https://img.shields.io/badge/license-0BSD-brightgreen.svg)](https://opensource.org/licenses/0BSD)
 [![Hackage](https://img.shields.io/hackage/v/sexpresso.svg)](http://hackage.haskell.org/package/sexpresso)
 
+# S-expresso is now in passive maintenance
+I will try my best to fix new issues or merge new pull requests, but I do not work on this project anymore.
+Expect some delay before I reply. If you wish to take over the project please contact me.
+
 # S-expresso
 
 S-expresso is a Haskell library designed to help you parse and print
diff --git a/sexpresso.cabal b/sexpresso.cabal
--- a/sexpresso.cabal
+++ b/sexpresso.cabal
@@ -1,11 +1,11 @@
 cabal-version: 1.12
 
--- This file has been generated from package.yaml by hpack version 0.34.4.
+-- This file has been generated from package.yaml by hpack version 0.34.5.
 --
 -- see: https://github.com/sol/hpack
 
 name:           sexpresso
-version:        1.2.0.0
+version:        1.2.1.0
 synopsis:       A flexible library for parsing and printing S-expression
 description:    Please see the README on GitHub at <https://github.com/archambaultv/sexpresso#readme>
 category:       Data
@@ -44,7 +44,7 @@
       base >=4.7 && <5
     , bifunctors ==5.5.*
     , containers >=0.5 && <0.7
-    , megaparsec >=7.0 && <9.1.0
+    , megaparsec >=7.0 && <9.3.0
     , recursion-schemes >=5.1 && <5.3
     , text >=0.2 && <1.3
   default-language: Haskell2010
@@ -65,7 +65,7 @@
       base >=4.7 && <5
     , bifunctors ==5.5.*
     , containers >=0.5 && <0.7
-    , megaparsec >=7.0 && <9.1.0
+    , megaparsec >=7.0 && <9.3.0
     , recursion-schemes >=5.1 && <5.3
     , sexpresso
     , smallcheck >=1.0
diff --git a/src/Data/SExpresso/Language/SchemeR5RS.hs b/src/Data/SExpresso/Language/SchemeR5RS.hs
--- a/src/Data/SExpresso/Language/SchemeR5RS.hs
+++ b/src/Data/SExpresso/Language/SchemeR5RS.hs
@@ -13,6 +13,7 @@
 -- R5RS datum (see 'Datum') by the function 'sexpr2Datum'.
 
 
+{-# LANGUAGE DeriveDataTypeable #-}
 {-# LANGUAGE OverloadedStrings #-}
 {-# LANGUAGE TypeFamilies #-}
 {-# LANGUAGE ScopedTypeVariables #-}
@@ -75,6 +76,7 @@
   ) where
 
 import Control.Monad (mzero)
+import Data.Data
 import Data.Maybe
 import Data.Proxy
 import Data.List
@@ -115,7 +117,7 @@
   | TCommaAt
   -- | The dot (.) symbol.
   | TDot
-  deriving (Eq, Show)
+  deriving (Eq, Show, Data)
 
 -- | The 'tokenParser' parses a 'SchemeToken'
 tokenParser :: (MonadParsec e s m, Token s ~ Char) => m SchemeToken
@@ -152,7 +154,7 @@
   STList
   -- | A vector
   | STVector
-  deriving (Eq, Show)
+  deriving (Eq, Show, Data)
 
 -- | The 'sexpr' defines a 'SExprParser' to parse a Scheme R5RS
 -- s-expression as an @'SExpr' 'SExprType' 'SchemeToken'@. If you also
@@ -184,7 +186,7 @@
            | DComma Datum
            | DCommaAt Datum
            | DVector [Datum]
-           deriving (Eq, Show)
+           deriving (Eq, Show, Data)
 
 -- | The 'sexpr2Datum' function takes a list of 'SchemeToken' and
 -- returns a list of 'Datum'. In case of failure it will report an
@@ -310,7 +312,7 @@
 
 ------------------------- Numbers -------------------------
 data Radix = R2 | R8 | R10 | R16
-           deriving (Eq, Show)
+           deriving (Eq, Show, Data)
 
 -- | A Scheme R5RS number is either exact or inexact. The paragraph
 -- 6.4.2 from the R5RS report should clarify the meaning of exact and
@@ -325,11 +327,11 @@
 -- exponent, or a \“#\” character in the place of a digit, otherwise it
 -- is exact.\"\"\"
 data Exactness = Exact | Inexact
-               deriving (Eq, Show)
+               deriving (Eq, Show, Data)
 
 -- | The 'Sign' datatype indicates if a number is positive ('Plus') or negative ('Minus')
 data Sign = Plus | Minus
-          deriving (Eq, Show)
+          deriving (Eq, Show, Data)
 
 -- | A Scheme R5RS number can have many # signs at the end. This type alias
 -- indicates the number of # signs parsed.
@@ -351,7 +353,7 @@
   | UIntPounds Integer Pounds
   -- | Integer made only of #. It can only appear as the third argument in numbers of the form @'SDecimal' _ _ _ _@.
   | UPounds Pounds
-  deriving (Eq, Show)
+  deriving (Eq, Show, Data)
 
 hasPounds :: UInteger -> Bool
 hasPounds (UInteger _) = False
@@ -374,12 +376,12 @@
   PDouble |
   -- | Suffix starting with l.
   PLong
-  deriving (Eq, Show)
+  deriving (Eq, Show, Data)
 
 -- | The 'Suffix' data type represents the suffix for a Scheme R5RS
 -- decimal number. It is a based 10 exponent.
 data Suffix = Suffix Precision Sign Integer
-            deriving (Eq, Show)
+            deriving (Eq, Show, Data)
 
 -- | The 'SReal' data type represents a Scheme R5RS real number.
 data SReal =
@@ -391,7 +393,7 @@
   -- | A signed decimal number. The first number appears before the
   -- dot, the second one after the dot.
   | SDecimal Sign UInteger UInteger (Maybe Suffix)
-  deriving (Eq, Show)
+  deriving (Eq, Show, Data)
 
 isInexactR :: SReal -> Bool
 isInexactR (SInteger _ i) = isInexactI i
@@ -406,7 +408,7 @@
   | CAngle SReal SReal
   -- | A complex number in absolute notation.
   | CAbsolute SReal SReal
-  deriving (Eq, Show)
+  deriving (Eq, Show, Data)
 
 isInexact :: Complex -> Bool
 isInexact (CReal s) = isInexactR s
@@ -415,7 +417,7 @@
 
 -- | A Scheme R5RS number is an exact or inexact complex number.
 data SchemeNumber = SchemeNumber Exactness Complex
-                  deriving (Eq, Show)
+                  deriving (Eq, Show, Data)
 
 -- | The 'number' parser parses a Scheme R5RS number.
 number :: (MonadParsec e s m, Token s ~ Char) => m SchemeNumber
diff --git a/src/Data/SExpresso/SExpr.hs b/src/Data/SExpresso/SExpr.hs
--- a/src/Data/SExpresso/SExpr.hs
+++ b/src/Data/SExpresso/SExpr.hs
@@ -13,7 +13,7 @@
 {-# LANGUAGE TemplateHaskell #-}
 {-# LANGUAGE KindSignatures #-}
 {-# LANGUAGE TypeFamilies #-}
-{-# LANGUAGE DeriveFunctor, DeriveFoldable, DeriveTraversable #-}
+{-# LANGUAGE DeriveFunctor, DeriveFoldable, DeriveTraversable, DeriveDataTypeable #-}
 
 
 module Data.SExpresso.SExpr
@@ -33,6 +33,7 @@
   where
 
 import Data.Bifunctor.TH
+import Data.Data
 import Data.Functor.Foldable.TH
 
 -- | The datatype 'SExpr' is the definition of an S-expression for the
@@ -43,7 +44,7 @@
 -- like source position for example.
 data SExpr b a = SList b [SExpr b a]
                | SAtom a
-               deriving (Eq, Show, Functor, Traversable, Foldable)
+               deriving (Eq, Show, Functor, Traversable, Foldable, Data)
 
 $(deriveBifunctor ''SExpr)
 $(deriveBifoldable ''SExpr)