diff --git a/indexation.cabal b/indexation.cabal
--- a/indexation.cabal
+++ b/indexation.cabal
@@ -1,5 +1,5 @@
 name: indexation
-version: 0.6.0.1
+version: 0.6.1
 category: Data
 synopsis: Tools for entity indexation
 description: A set of tools for indexing entities
@@ -40,6 +40,7 @@
     cereal >=0.5.5 && <0.6,
     cereal-vector >=0.2.0.1 && <0.3,
     contravariant >=1.4 && <2,
+    deepseq >=1.4.3 && <2,
     deferred-folds >=0.9.6 && <0.10,
     dense-int-set >=0.1.5 && <0.2,
     focus >=1.0.1 && <1.1,
diff --git a/library/Indexation/Instances.hs b/library/Indexation/Instances.hs
--- a/library/Indexation/Instances.hs
+++ b/library/Indexation/Instances.hs
@@ -11,6 +11,8 @@
 deriving instance Eq (Index a)
 deriving instance Ord (Index a)
 deriving instance Hashable (Index a)
+deriving instance Generic (Index a)
+instance NFData (Index a)
 
 instance Show (IndexSet a) where
   show = show . (\ (IndexSet x) -> x)
diff --git a/library/Indexation/Prelude.hs b/library/Indexation/Prelude.hs
--- a/library/Indexation/Prelude.hs
+++ b/library/Indexation/Prelude.hs
@@ -142,6 +142,10 @@
 -------------------------
 import DenseIntSet as Exports (DenseIntSet)
 
+-- deepseq
+-------------------------
+import Control.DeepSeq as Exports
+
 -- 
 -------------------------
 import qualified Data.Vector.Unboxed as UnboxedVector