diff --git a/Data/Symbol.hs b/Data/Symbol.hs
--- a/Data/Symbol.hs
+++ b/Data/Symbol.hs
@@ -1,74 +1,16 @@
 -- |
 -- Module      :  Data.Symbol
--- Copyright   :  (c) Harvard University 2009-2012
---             :  (c) Geoffrey Mainland 2011-2012
+-- Copyright   :  (c) Harvard University 2009-2011
+--             :  (c) Geoffrey Mainland 2011-2013
 -- License     :  BSD-style
 -- Maintainer  :  mainland@eecs.harvard.edu
 
-{-# LANGUAGE CPP #-}
-{-# LANGUAGE DeriveDataTypeable #-}
+{-# LANGUAGE Trustworthy #-}
 
 module Data.Symbol (
-    Symbol(..),
+    Symbol,
     intern,
     unintern
   ) where
 
-import Control.Concurrent.MVar
-import Control.DeepSeq
-import Data.Generics (Data, Typeable)
-#if __GLASGOW_HASKELL__ >= 608
-import Data.String
-#endif /* __GLASGOW_HASKELL__ >= 608 */
-import qualified Data.Map as Map
-import System.IO.Unsafe (unsafePerformIO)
-
-data Symbol =  -- | Unique identifier and the string itself
-               Symbol {-# UNPACK #-} !Int !String
-#if defined(__GLASGOW_HASKELL__)
-  deriving (Data, Typeable)
-#endif /* defined(__GLASGOW_HASKELL__) */
-
-instance Eq Symbol where
-    (Symbol i1 _) == (Symbol i2 _) = i1 == i2
-
-instance Ord Symbol where
-    compare (Symbol i1 _) (Symbol i2 _) = compare i1 i2
-
-instance Show Symbol where
-    showsPrec _ (Symbol _ s) = showString s
-
-#if __GLASGOW_HASKELL__ >= 608
-instance IsString Symbol where
-    fromString = intern
-#endif /* __GLASGOW_HASKELL__ >= 608 */
-
-data SymbolEnv = SymbolEnv
-    { uniq    :: {-# UNPACK #-} !Int
-    , symbols :: !(Map.Map String Symbol)
-    }
-
-symbolEnv :: MVar SymbolEnv
-{-# NOINLINE symbolEnv #-}
-symbolEnv = unsafePerformIO $ newMVar $ SymbolEnv 1 Map.empty
-
--- We @seq@ @s@ so that we can guarantee that when we perform the lookup we
--- won't potentially have to evaluate a thunk that might itself call @intern@,
--- leading to a deadlock.
-
--- |Intern a string to produce a 'Symbol'.
-intern :: String -> Symbol
-{-# NOINLINE intern #-}
-intern s = s `deepseq` unsafePerformIO $ modifyMVar symbolEnv $ \env -> do
-    case Map.lookup s (symbols env) of
-      Nothing  -> do let sym  = Symbol (uniq env) s
-                     let env' = env { uniq    = uniq env + 1,
-                                      symbols = Map.insert s sym
-                                                (symbols env)
-                                    }
-                     env' `seq` return (env', sym)
-      Just sym -> return (env, sym)
-
--- |Return the 'String' associated with a 'Symbol'.
-unintern :: Symbol -> String
-unintern (Symbol _ s) = s
+import Data.Symbol.Unsafe
diff --git a/Data/Symbol/Unsafe.hs b/Data/Symbol/Unsafe.hs
new file mode 100644
--- /dev/null
+++ b/Data/Symbol/Unsafe.hs
@@ -0,0 +1,74 @@
+-- |
+-- Module      :  Data.Symbol.Unsafe
+-- Copyright   :  (c) Harvard University 2009-2011
+--             :  (c) Geoffrey Mainland 2011-2013
+-- License     :  BSD-style
+-- Maintainer  :  mainland@eecs.harvard.edu
+
+{-# LANGUAGE CPP #-}
+{-# LANGUAGE DeriveDataTypeable #-}
+
+module Data.Symbol.Unsafe (
+    Symbol(..),
+    intern,
+    unintern
+  ) where
+
+import Control.Concurrent.MVar
+import Control.DeepSeq
+import Data.Generics (Data, Typeable)
+#if __GLASGOW_HASKELL__ >= 608
+import Data.String
+#endif /* __GLASGOW_HASKELL__ >= 608 */
+import qualified Data.Map as Map
+import System.IO.Unsafe (unsafePerformIO)
+
+data Symbol =  -- | Unique identifier and the string itself
+               Symbol {-# UNPACK #-} !Int !String
+#if defined(__GLASGOW_HASKELL__)
+  deriving (Data, Typeable)
+#endif /* defined(__GLASGOW_HASKELL__) */
+
+instance Eq Symbol where
+    (Symbol i1 _) == (Symbol i2 _) = i1 == i2
+
+instance Ord Symbol where
+    compare (Symbol i1 _) (Symbol i2 _) = compare i1 i2
+
+instance Show Symbol where
+    showsPrec _ (Symbol _ s) = showString s
+
+#if __GLASGOW_HASKELL__ >= 608
+instance IsString Symbol where
+    fromString = intern
+#endif /* __GLASGOW_HASKELL__ >= 608 */
+
+data SymbolEnv = SymbolEnv
+    { uniq    :: {-# UNPACK #-} !Int
+    , symbols :: !(Map.Map String Symbol)
+    }
+
+symbolEnv :: MVar SymbolEnv
+{-# NOINLINE symbolEnv #-}
+symbolEnv = unsafePerformIO $ newMVar $ SymbolEnv 1 Map.empty
+
+-- We @'deepseq' s@ so that we can guarantee that when we perform the lookup we
+-- won't potentially have to evaluate a thunk that might itself call @'intern'@,
+-- leading to a deadlock.
+
+-- |Intern a string to produce a 'Symbol'.
+intern :: String -> Symbol
+{-# NOINLINE intern #-}
+intern s = s `deepseq` unsafePerformIO $ modifyMVar symbolEnv $ \env -> do
+    case Map.lookup s (symbols env) of
+      Nothing  -> do let sym  = Symbol (uniq env) s
+                     let env' = env { uniq    = uniq env + 1,
+                                      symbols = Map.insert s sym
+                                                (symbols env)
+                                    }
+                     env' `seq` return (env', sym)
+      Just sym -> return (env, sym)
+
+-- |Return the 'String' associated with a 'Symbol'.
+unintern :: Symbol -> String
+unintern (Symbol _ s) = s
diff --git a/LICENSE b/LICENSE
--- a/LICENSE
+++ b/LICENSE
@@ -1,4 +1,4 @@
-Copyright (c) 2006-2010
+Copyright (c) 2006-2011
         The President and Fellows of Harvard College.
 
 Redistribution and use in source and binary forms, with or without
@@ -25,7 +25,7 @@
 OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 SUCH DAMAGE.
 
-Copyright (c) 2011-2012, Geoffrey Mainland
+Copyright (c) 2011-2013, Geoffrey Mainland
 All rights reserved.
 
 Redistribution and use in source and binary forms, with or without modification,
diff --git a/symbol.cabal b/symbol.cabal
--- a/symbol.cabal
+++ b/symbol.cabal
@@ -1,10 +1,10 @@
 name:           symbol
-version:        0.1.4
+version:        0.2.0
 cabal-version:  >= 1.6
 license:        BSD3
 license-file:   LICENSE
-copyright:      (c) 2006-2010 Harvard University
-		(c) 2011-2012 Geoffrey Mainland
+copyright:      (c) 2006-2011 Harvard University
+		(c) 2011-2013 Geoffrey Mainland
 author:         Geoffrey Mainland <mainland@eecs.harvard.edu>
 maintainer:     mainland@eecs.harvard.edu
 stability:      alpha
@@ -20,6 +20,7 @@
 library
   exposed-modules:
     Data.Symbol
+    Data.Symbol.Unsafe
 
   build-depends:
     base       >= 4   && < 5,