diff --git a/hw-prim.cabal b/hw-prim.cabal
--- a/hw-prim.cabal
+++ b/hw-prim.cabal
@@ -1,5 +1,5 @@
 name:                   hw-prim
-version:                0.3.0.4
+version:                0.3.0.5
 synopsis:               Primitive functions and data types
 description:            Please see README.md
 homepage:               http://github.com/haskell-works/hw-prim#readme
@@ -50,6 +50,7 @@
                       , HaskellWorks.Data.TreeCursor
                       , HaskellWorks.Data.Uncons
                       , HaskellWorks.Data.Unsign
+                      , HaskellWorks.Data.Vector.AsVector64
                       , HaskellWorks.Data.Vector.BoxedVectorLike
                       , HaskellWorks.Data.Vector.StorableVectorLike
                       , HaskellWorks.Data.Widen
diff --git a/src/HaskellWorks/Data/Vector/AsVector64.hs b/src/HaskellWorks/Data/Vector/AsVector64.hs
new file mode 100644
--- /dev/null
+++ b/src/HaskellWorks/Data/Vector/AsVector64.hs
@@ -0,0 +1,13 @@
+{-# LANGUAGE FlexibleInstances #-}
+module HaskellWorks.Data.Vector.AsVector64
+  ( AsVector64(..)
+  ) where
+
+import qualified Data.Vector.Storable as DVS
+import           Data.Word
+
+class AsVector64 a where
+  asVector64 :: a -> DVS.Vector Word64
+
+instance AsVector64 (DVS.Vector Word64) where
+  asVector64 = id