diff --git a/Data/Aeson/Types.hs b/Data/Aeson/Types.hs
--- a/Data/Aeson/Types.hs
+++ b/Data/Aeson/Types.hs
@@ -212,12 +212,19 @@
              deriving (Eq, Show, Typeable, Data)
 
 instance NFData Value where
-    rnf (Object o) = rnf o
+    rnf (Object o) = obj_rnf o
     rnf (Array a)  = V.foldl' (\x y -> rnf y `seq` x) () a
     rnf (String s) = rnf s
     rnf (Number n) = case n of I i -> rnf i; D d -> rnf d
     rnf (Bool b)   = rnf b
     rnf Null       = ()
+
+obj_rnf :: (NFData k, NFData v) => Map k v -> ()
+#if MIN_VERSION_containers(0,4,2)
+obj_rnf = rnf
+#else
+obj_rnf = rnf . M.toList
+#endif
 
 instance IsString Value where
     fromString = String . pack
diff --git a/aeson.cabal b/aeson.cabal
--- a/aeson.cabal
+++ b/aeson.cabal
@@ -1,5 +1,5 @@
 name:            aeson
-version:         0.3.2.12
+version:         0.3.2.13
 license:         BSD3
 license-file:    LICENSE
 category:        Text, Web, JSON
@@ -121,7 +121,7 @@
     blaze-textual >= 0.2.0.2,
     bytestring,
     containers,
-    deepseq < 1.2,
+    deepseq,
     hashable >= 1.1.2.0,
     mtl,
     old-locale,