diff --git a/flat-mcmc.cabal b/flat-mcmc.cabal
--- a/flat-mcmc.cabal
+++ b/flat-mcmc.cabal
@@ -1,5 +1,5 @@
 name:                flat-mcmc
-version:             1.0.1
+version:             1.1.1
 synopsis:            Painless general-purpose sampling.
 homepage:            http://jtobin.github.com/flat-mcmc
 license:             MIT
@@ -52,12 +52,12 @@
   hs-source-dirs:   lib
   exposed-modules:  Numeric.MCMC.Flat
   build-depends:
-      base             <  5
+      base             >  4     && < 6
     , mcmc-types       >= 1.0.1 && < 2
-    , monad-par
-    , monad-par-extras
+    , monad-par        >= 0.3.4.7 && < 1
+    , monad-par-extras >= 0.3.3 && < 1
     , mwc-probability  >= 1.0.1 && < 2
-    , pipes            >= 4 && < 5
+    , pipes            >  4     && < 5
     , primitive
     , transformers
     , vector
@@ -70,7 +70,7 @@
   ghc-options:
     -rtsopts -threaded
   build-depends:
-      base              < 5
+      base
     , flat-mcmc
     , vector
 
@@ -82,7 +82,7 @@
   ghc-options:
     -rtsopts -threaded
   build-depends:
-      base              < 5
+      base
     , flat-mcmc
     , vector
 
diff --git a/lib/Numeric/MCMC/Flat.hs b/lib/Numeric/MCMC/Flat.hs
--- a/lib/Numeric/MCMC/Flat.hs
+++ b/lib/Numeric/MCMC/Flat.hs
@@ -64,7 +64,7 @@
     . V.map show
     $ chainPosition
 
-type Particle = Vector Double
+type Particle = U.Vector Double
 
 type Ensemble = Vector Particle
 
@@ -73,13 +73,13 @@
   transform z = 0.5 * (z + 1) ^ (2 :: Int)
 
 stretch :: Particle -> Particle -> Double -> Particle
-stretch p0 p1 z = V.zipWith (+) (V.map (* z) p0) (V.map (* (1 - z)) p1)
+stretch p0 p1 z = U.zipWith (+) (U.map (* z) p0) (U.map (* (1 - z)) p1)
 
 acceptProb :: Target Particle -> Particle -> Particle -> Double -> Double
 acceptProb target particle proposal z =
     lTarget target proposal
   - lTarget target particle
-  + log z * (fromIntegral (V.length particle) - 1)
+  + log z * (fromIntegral (U.length particle) - 1)
 
 move :: Target Particle -> Particle -> Particle -> Double -> Double -> Particle
 move target p0 p1 z zc =
diff --git a/test/BNN.hs b/test/BNN.hs
--- a/test/BNN.hs
+++ b/test/BNN.hs
@@ -3,18 +3,19 @@
 module Main where
 
 import Numeric.MCMC.Flat
-import Data.Vector (Vector, toList, fromList)
+import qualified Data.Vector.Unboxed as U (Vector, toList, fromList)
+import qualified Data.Vector as V (fromList)
 
-bnn :: Vector Double -> Double
+bnn :: Particle -> Double
 bnn xs = -0.5 * (x0 ^ 2 * x1 ^ 2 + x0 ^ 2 + x1 ^ 2 - 8 * x0 - 8 * x1) where
-  [x0, x1] = toList xs
+  [x0, x1] = U.toList xs
 
 ensemble :: Ensemble
-ensemble = fromList [
-    fromList [negate 1.0, negate 1.0]
-  , fromList [negate 1.0, 1.0]
-  , fromList [1.0, negate 1.0]
-  , fromList [1.0, 1.0]
+ensemble = V.fromList [
+    U.fromList [negate 1.0, negate 1.0]
+  , U.fromList [negate 1.0, 1.0]
+  , U.fromList [1.0, negate 1.0]
+  , U.fromList [1.0, 1.0]
   ]
 
 main :: IO ()
diff --git a/test/Rosenbrock.hs b/test/Rosenbrock.hs
--- a/test/Rosenbrock.hs
+++ b/test/Rosenbrock.hs
@@ -3,18 +3,19 @@
 module Main where
 
 import Numeric.MCMC.Flat
-import Data.Vector (Vector, toList, fromList)
+import qualified Data.Vector.Unboxed as U (Vector, toList, fromList)
+import qualified Data.Vector as V (fromList)
 
-rosenbrock :: Vector Double -> Double
+rosenbrock :: Particle -> Double
 rosenbrock xs = negate (5  *(x1 - x0 ^ 2) ^ 2 + 0.05 * (1 - x0) ^ 2) where
-  [x0, x1] = toList xs
+  [x0, x1] = U.toList xs
 
 ensemble :: Ensemble
-ensemble = fromList [
-    fromList [negate 1.0, negate 1.0]
-  , fromList [negate 1.0, 1.0]
-  , fromList [1.0, negate 1.0]
-  , fromList [1.0, 1.0]
+ensemble = V.fromList [
+    U.fromList [negate 1.0, negate 1.0]
+  , U.fromList [negate 1.0, 1.0]
+  , U.fromList [1.0, negate 1.0]
+  , U.fromList [1.0, 1.0]
   ]
 
 main :: IO ()