diff --git a/hw-bits.cabal b/hw-bits.cabal
--- a/hw-bits.cabal
+++ b/hw-bits.cabal
@@ -1,5 +1,5 @@
 name:                   hw-bits
-version:                0.5.0.0
+version:                0.5.0.1
 synopsis:               Bit manipulation
 description:            Please see README.md
 homepage:               http://github.com/haskell-works/hw-bits#readme
@@ -14,6 +14,10 @@
 extra-source-files:     README.md
 cabal-version:          >= 1.22
 
+Flag sse42
+    Description:        Enable SSE 4.2 optimisations.
+    Default:            True
+
 library
   hs-source-dirs:       src
   exposed-modules:      HaskellWorks.Data.Bits
@@ -42,14 +46,18 @@
   build-depends:        base                          >= 4          && < 5
                       , bytestring
                       , hw-int                        >= 0.0.0.1
-                      , hw-prim                       >= 0.4.0.0
+                      , hw-prim                       >= 0.4.0.3
                       , hw-string-parse               >= 0.0.0.1
                       , safe
                       , vector
 
   default-language:     Haskell2010
-  ghc-options:          -Wall -O2 -msse4.2
 
+  if flag(sse42)
+    ghc-options:          -Wall -O2 -msse4.2
+  else
+    ghc-options:          -Wall -O2
+
 test-suite hw-bits-test
   type:                 exitcode-stdio-1.0
   hs-source-dirs:       test
@@ -63,7 +71,7 @@
                       , bytestring
                       , hspec
                       , hw-bits
-                      , hw-prim                       >= 0.4.0.0
+                      , hw-prim                       >= 0.4.0.3
                       , QuickCheck
                       , vector
   ghc-options:          -threaded -rtsopts -with-rtsopts=-N -Wall
@@ -77,7 +85,10 @@
     Type: exitcode-stdio-1.0
     HS-Source-Dirs: bench
     Main-Is: Main.hs
-    GHC-Options: -Wall -O2 -msse4.2
+    if flag(sse42)
+      GHC-Options: -Wall -O2 -msse4.2
+    else
+      GHC-Options: -Wall -O2
     Default-Language: Haskell2010
     Build-Depends:      base                          >= 4          && < 5
                       , criterion