diff --git a/tensorflow/src/TensorFlow/Types.hs b/tensorflow/src/TensorFlow/Types.hs
index b5fd115..32246d4 100644
--- a/tensorflow/src/TensorFlow/Types.hs
+++ b/tensorflow/src/TensorFlow/Types.hs
@@ -262,7 +262,7 @@ instance TensorDataType S.Vector Bool where
       where
         fromBool x = if x then 1 else 0 :: Word8
 
-instance {-# OVERLAPPABLE #-} (Storable a, TensorDataType S.Vector a)
+instance {-# OVERLAPPABLE #-} (TensorType a, Storable a, TensorDataType S.Vector a)
     => TensorDataType V.Vector a where
     decodeTensorData = (S.convert :: S.Vector a -> V.Vector a) . decodeTensorData
     encodeTensorData x = encodeTensorData x . (S.convert :: V.Vector a -> S.Vector a)
@@ -329,7 +329,7 @@ newtype Scalar a = Scalar {unScalar :: a}
     deriving (Show, Eq, Ord, Num, Fractional, Floating, Real, RealFloat,
               RealFrac, IsString)
 
-instance TensorDataType V.Vector a => TensorDataType Scalar a where
+instance (TensorType a, TensorDataType V.Vector a) => TensorDataType Scalar a where
     decodeTensorData = Scalar . headFromSingleton . decodeTensorData
     encodeTensorData x (Scalar y) = encodeTensorData x (V.fromList [y])