diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,9 @@
 # Changelog for [`clash-prelude` package](http://hackage.haskell.org/package/clash-prelude)
 
+## 0.7.1 *March 25th 2015*
+* Fixes bugs:
+  * Fix laziness bug in Vector.(!!) and Vector.replace
+
 ## 0.7 *March 13th 2015*
 * New features:
   * Switch types of 'bundle' and 'bundle'', and 'unbundle' and 'unbundle''.
diff --git a/clash-prelude.cabal b/clash-prelude.cabal
--- a/clash-prelude.cabal
+++ b/clash-prelude.cabal
@@ -1,5 +1,5 @@
 Name:                 clash-prelude
-Version:              0.7
+Version:              0.7.1
 Synopsis:             CAES Language for Synchronous Hardware - Prelude library
 Description:
   CλaSH (pronounced ‘clash’) is a functional hardware description language that
diff --git a/src/CLaSH/Sized/Vector.hs b/src/CLaSH/Sized/Vector.hs
--- a/src/CLaSH/Sized/Vector.hs
+++ b/src/CLaSH/Sized/Vector.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE BangPatterns         #-}
 {-# LANGUAGE DataKinds            #-}
 {-# LANGUAGE FlexibleContexts     #-}
 {-# LANGUAGE GADTs                #-}
@@ -426,7 +427,7 @@
 zipWith f (x :> xs) ys = f x (head ys) :> zipWith f xs (tail ys)
 
 {-# INLINABLE foldr #-}
--- | 'vfoldr', applied to a binary operator, a starting value (typically
+-- | 'foldr', applied to a binary operator, a starting value (typically
 -- the right-identity of the operator), and a vector, reduces the vector
 -- using the binary operator, from right to left:
 --
@@ -638,9 +639,9 @@
                                     , " is larger than maximum index "
                                     , show (maxIndex xs)
                                     ])
-    sub (y:>ys) n = if isTrue# (n ==# 0#)
-                    then y
-                    else sub ys (n -# 1#)
+    sub (y:>(!ys)) n = if isTrue# (n ==# 0#)
+                       then y
+                       else sub ys (n -# 1#)
 
 {-# INLINE (!!) #-}
 -- | Vector index (subscript) operator.
@@ -687,9 +688,9 @@
                                       , " is larger than maximum index "
                                       , show (maxIndex xs)
                                       ])
-    sub (y:>ys) n b = if isTrue# (n ==# 0#)
-                      then b :> ys
-                      else y :> sub ys (n -# 1#) b
+    sub (y:>(!ys)) n b = if isTrue# (n ==# 0#)
+                         then b :> ys
+                         else y :> sub ys (n -# 1#) b
 
 {-# INLINE replace #-}
 -- | Replace an element of a vector at the given index (subscript).