diff --git a/Numeric/FFT/Vector/Base.hsc b/Numeric/FFT/Vector/Base.hsc
--- a/Numeric/FFT/Vector/Base.hsc
+++ b/Numeric/FFT/Vector/Base.hsc
@@ -12,6 +12,7 @@
             planOutputSize,
             execute,
             executeM,
+            withPlanner,
             -- * Unsafe C stuff
             CFlags,
             CPlan,
@@ -27,9 +28,10 @@
 import qualified Data.Vector.Storable as VS
 import qualified Data.Vector.Storable.Mutable as MS
 import Data.Vector.Generic as V hiding (forM_)
-import Data.Vector.Generic.Mutable as M
+import Data.Vector.Generic.Mutable as M hiding (unsafeModify)
 import Data.List as L
-import Control.Monad.Primitive (RealWorld,PrimMonad(..),
+import Control.Concurrent.MVar
+import Control.Monad.Primitive (RealWorld,PrimMonad(..), PrimBase,
             unsafePrimToPrim, unsafePrimToIO)
 import Control.Monad(forM_)
 import Foreign (Storable(..), Ptr, FunPtr,
@@ -125,7 +127,7 @@
 -- If @'planInputSize' p \/= length vIn@ or @'planOutputSize' p \/= length vOut@,
 -- then calling @unsafeExecuteM p vIn vOut@ will throw an exception.
 executeM :: forall m v a b .
-        (PrimMonad m, MVector v a, MVector v b, Storable a, Storable b)
+        (PrimBase m, MVector v a, MVector v b, Storable a, Storable b)
             => Plan a b -- ^ The plan to run.
             -> v (PrimState m) a  -- ^ The input vector.
                     -> v (PrimState m) b -- ^ The output vector.
@@ -248,3 +250,16 @@
 unsafeModify :: (Storable a)
                 => MS.MVector RealWorld a -> Int -> (a -> a) -> IO ()
 unsafeModify v k f = MS.unsafeRead v k >>= MS.unsafeWrite v k . f
+
+plannerLock :: MVar ()
+plannerLock = unsafePerformIO $ newMVar ()
+{-# NOINLINE plannerLock #-}
+
+-- | Calls to the FFTW planner are non-reentrant. Here we take a mutex to
+-- ensure thread safety.
+withPlanner :: IO a -> IO a
+withPlanner action = do
+    takeMVar plannerLock
+    res <- action
+    putMVar plannerLock ()
+    return res
diff --git a/Numeric/FFT/Vector/Unnormalized.hsc b/Numeric/FFT/Vector/Unnormalized.hsc
--- a/Numeric/FFT/Vector/Unnormalized.hsc
+++ b/Numeric/FFT/Vector/Unnormalized.hsc
@@ -63,7 +63,7 @@
             inputSize = id,
             outputSize = id,
             creationSizeFromInput = id,
-            makePlan = \n a b -> fftw_plan_dft_1d n a b d,
+            makePlan = \n a b -> withPlanner . fftw_plan_dft_1d n a b d,
             normalization = const id
             }
 
@@ -86,7 +86,7 @@
             inputSize = id,
             outputSize = \n -> n `div` 2 + 1,
             creationSizeFromInput = id,
-            makePlan = fftw_plan_dft_r2c_1d,
+            makePlan = \n a b -> withPlanner . fftw_plan_dft_r2c_1d n a b,
             normalization = const id
         }
 
@@ -103,7 +103,7 @@
             inputSize = \n -> n `div` 2 + 1,
             outputSize = id,
             creationSizeFromInput = \n -> 2 * (n-1),
-            makePlan = fftw_plan_dft_c2r_1d,
+            makePlan = \n a b -> withPlanner . fftw_plan_dft_c2r_1d n a b,
             normalization = const id
         }
 
@@ -112,7 +112,7 @@
                     inputSize = id,
                     outputSize = id,
                     creationSizeFromInput = id,
-                    makePlan = \n a b -> fftw_plan_r2r_1d n a b kind,
+                    makePlan = \n a b -> withPlanner . fftw_plan_r2r_1d n a b kind,
                     normalization = const id
                 }
 
diff --git a/vector-fftw.cabal b/vector-fftw.cabal
--- a/vector-fftw.cabal
+++ b/vector-fftw.cabal
@@ -1,10 +1,10 @@
 Name:                vector-fftw
 
-Version:             0.1.3.2
+Version:             0.1.3.3
 License:             BSD3
 License-file:        LICENSE
 Author:              Judah Jacobson
-Maintainer:          Judah Jacobson <judah.jacobson@gmail.com>
+Maintainer:          Ben Gamari <ben@smart-cactus.org>
 Copyright:           (c) Judah Jacobson, 2010
 Category:            Math
 Build-type:          Simple
@@ -22,12 +22,10 @@
                      .
                       - "Numeric.FFT.Vector.Unitary" additionally scales all transforms to preserve the L2 (sum-of-squares) norm of the
                         input.
-                     .
-                     Note that this package is currently not thread-safe.
 
 source-repository head
     type:   git
-    location: https://github.com/judah/vector-fftw
+    location: https://github.com/bgamari/vector-fftw
 
 
 Library
@@ -40,9 +38,9 @@
   Other-modules:
         Numeric.FFT.Vector.Base
   
-  Build-depends: base>=4.3 && < 4.8,
-                 vector>=0.9 && < 0.11,
-                 primitive>=0.4 && < 0.6,
+  Build-depends: base>=4.3 && < 4.9,
+                 vector>=0.9 && < 0.12,
+                 primitive>=0.6 && < 0.7,
                  storable-complex==0.2.*
   Extra-libraries: fftw3