diff --git a/hmatrix-gsl.cabal b/hmatrix-gsl.cabal
--- a/hmatrix-gsl.cabal
+++ b/hmatrix-gsl.cabal
@@ -1,5 +1,5 @@
 Name:               hmatrix-gsl
-Version:            0.19.0.0
+Version:            0.19.0.1
 Synopsis:           Numerical computation
 Description:        Purely functional interface to selected numerical computations,
                     internally implemented using GSL.
diff --git a/src/Numeric/GSL/Internal.hs b/src/Numeric/GSL/Internal.hs
--- a/src/Numeric/GSL/Internal.hs
+++ b/src/Numeric/GSL/Internal.hs
@@ -131,8 +131,7 @@
 ww2 w1 o1 w2 o2 f = w1 o1 $ \a1 -> w2 o2 $ \a2 -> f a1 a2
 
 vec x f = unsafeWith x $ \p -> do
-    let v g = do
-        g (fi $ V.length x) p
+    let v g = g (fi $ V.length x) p
     f v
 {-# INLINE vec #-}