diff --git a/CHANGES b/CHANGES
--- a/CHANGES
+++ b/CHANGES
@@ -1,3 +1,5 @@
+0.5.3: Add 'zeroExtend' and 'signExtend'
+0.5.2: Fix right shift
 0.5.1:  Add 'define' commands
 0.5:    Adds more bit-wise operations
 0.4:    Fixes definiiton of `geq`
diff --git a/SimpleSMT.hs b/SimpleSMT.hs
--- a/SimpleSMT.hs
+++ b/SimpleSMT.hs
@@ -106,6 +106,8 @@
   , bvShl
   , bvLShr
   , bvAShr
+  , signExtend
+  , zeroExtend
 
     -- ** Arrays
   , select
@@ -615,6 +617,15 @@
 concat :: SExpr -> SExpr -> SExpr
 concat x y = fun "concat" [x,y]
 
+-- | Extend to the signed equivalent bitvector by @i@ bits
+signExtend :: Integer -> SExpr -> SExpr
+signExtend i x = List [ fam "sign_extend" [i], x ]
+
+-- | Extend with zeros to the unsigned equivalent bitvector
+-- by @i@ bits
+zeroExtend :: Integer -> SExpr -> SExpr
+zeroExtend i x = List [ fam "zero_extend" [i], x ]
+
 -- | Extract a sub-sequence of a bit vector.
 extract :: SExpr -> Integer -> Integer -> SExpr
 extract x y z = List [ fam "extract" [y,z], x ]
@@ -683,6 +694,7 @@
 -- | Arithemti shift right (copies most significant bit).
 bvAShr :: SExpr {- ^ value -} -> SExpr {- ^ shift amount -} -> SExpr
 bvAShr x y = fun "bvashr" [x,y]
+
 
 -- | Get an elemeent of an array.
 select :: SExpr {- ^ array -} -> SExpr {- ^ index -} -> SExpr
diff --git a/simple-smt.cabal b/simple-smt.cabal
--- a/simple-smt.cabal
+++ b/simple-smt.cabal
@@ -1,5 +1,5 @@
 name:                simple-smt
-version:             0.5.2
+version:             0.5.3
 synopsis:            A simple way to interact with an SMT solver process.
 description:         A simple way to interact with an SMT solver process.
 license:             BSD3