diff --git a/Data/Constraint.hs b/Data/Constraint.hs
--- a/Data/Constraint.hs
+++ b/Data/Constraint.hs
@@ -15,6 +15,7 @@
 {-# LANGUAGE CPP #-}
 #if defined(__GLASGOW_HASKELL__) && __GLASGOW_HASKELL__ >= 707
 {-# LANGUAGE AllowAmbiguousTypes #-}
+{-# LANGUAGE DeriveDataTypeable #-}
 {-# LANGUAGE RoleAnnotations #-}
 #endif
 -----------------------------------------------------------------------------
@@ -55,14 +56,32 @@
 import Data.Monoid
 import Data.Complex
 import Data.Ratio
+#if defined(__GLASGOW_HASKELL__) && __GLASGOW_HASKELL__ >= 707
+import Data.Data
+#endif
 import GHC.Prim (Constraint)
 
 -- | Capture a dictionary for a given constraint
 data Dict :: Constraint -> * where
   Dict :: a => Dict a
-
 #if defined(__GLASGOW_HASKELL__) && __GLASGOW_HASKELL__ >= 707
+  deriving Typeable
+
 type role Dict nominal
+
+instance (Typeable p, p) => Data (Dict p) where
+  gfoldl _ z Dict = z Dict
+  toConstr _ = dictConstr
+  gunfold _ z c = case constrIndex c of
+    1 -> z Dict
+    _ -> error "gunfold"
+  dataTypeOf _ = dictDataType
+
+dictConstr :: Constr
+dictConstr = mkConstr dictDataType "Dict" [] Prefix
+
+dictDataType :: DataType
+dictDataType = mkDataType "Data.Constraint.Dict" [dictConstr]
 #endif
 
 deriving instance Eq (Dict a)
@@ -72,10 +91,28 @@
 infixr 9 :-
 newtype a :- b = Sub (a => Dict b)
 #if defined(__GLASGOW_HASKELL__) && __GLASGOW_HASKELL__ >= 707
+  deriving Typeable
+
 type role (:-) nominal nominal
-#endif
 
-#if defined(__GLASGOW_HASKELL__) && __GLASGOW_HASKELL__ >= 707
+-- TODO: _proper_ Data for (p :- q) requires (:-) to be cartesian closed.
+-- This is admissable, but not present by default
+
+-- constraint should be instance (Typeable p, Typeable q, p |- q) => Data (p :- q)
+instance (Typeable p, Typeable q, p, q) => Data (p :- q) where
+  gfoldl _ z (Sub Dict) = z (Sub Dict)
+  toConstr _ = subConstr
+  gunfold _ z c = case constrIndex c of
+    1 -> z (Sub Dict)
+    _ -> error "gunfold"
+  dataTypeOf _ = subDataType
+
+subConstr :: Constr
+subConstr = mkConstr dictDataType "Sub" [] Prefix
+
+subDataType :: DataType
+subDataType = mkDataType "Data.Constraint.:-" [subConstr]
+
 instance Category (:-) where
   id  = refl
   (.) = trans
@@ -356,4 +393,3 @@
 instance a => Monoid (Dict a) where
   mappend Dict Dict = Dict
   mempty = Dict
-
diff --git a/constraints.cabal b/constraints.cabal
--- a/constraints.cabal
+++ b/constraints.cabal
@@ -1,6 +1,6 @@
 name:          constraints
 category:      Constraints
-version:       0.3.5
+version:       0.4
 license:       BSD3
 cabal-version: >= 1.10
 license-file:  LICENSE
@@ -22,7 +22,7 @@
 
 library
   default-language: Haskell2010
-  other-extensions
+  other-extensions:
     FunctionalDependencies,
     ScopedTypeVariables,
     StandaloneDeriving,