diff --git a/hxt.cabal b/hxt.cabal
--- a/hxt.cabal
+++ b/hxt.cabal
@@ -1,6 +1,6 @@
 -- arch-tag: Haskell XML Toolbox main description file
 Name:           hxt
-Version:        9.1.1
+Version:        9.1.2
 Synopsis:       A collection of tools for processing XML with Haskell.
 Description:    The Haskell XML Toolbox bases on the ideas of HaXml and HXML,
                 but introduces a more general approach for processing XML with Haskell.
@@ -15,7 +15,7 @@
                 hxt-curl, hxt-tagsoup, hxt-relaxng, hxt-xpath, hxt-xslt, hxt-regex-xmlschema contain the extensions.
                 hxt-unicode contains encoding and decoding functions,
                 hxt-charproperties char properties for unicode and XML.
-License:        OtherLicense
+License:        MIT
 License-file:   LICENSE
 Author:         Uwe Schmidt, Martin Schmidt, Torben Kuseler
 Maintainer:     Uwe Schmidt <uwe@fh-wedel.de>
@@ -176,6 +176,6 @@
                 deepseq    >= 1.1 && < 2,
                 bytestring >= 0.9 && < 1,
                 binary     >= 0.5 && < 1,
-                hxt-charproperties  >= 9.1 && < 10,
-                hxt-unicode         >= 9   && < 10,
-                hxt-regex-xmlschema >= 9   && < 10
+                hxt-charproperties  >= 9.1    && < 10,
+                hxt-unicode         >= 9.0.1  && < 10,
+                hxt-regex-xmlschema >= 9      && < 10
diff --git a/src/Data/Atom.hs b/src/Data/Atom.hs
--- a/src/Data/Atom.hs
+++ b/src/Data/Atom.hs
@@ -32,8 +32,8 @@
    up in the table of atoms. If it is already there, the value in the map is used as atom, else
    the new @ByteString@ is inserted into the map.
 
-   Of course the implementation of this name cache uses @unsavePerformIO@ and @MVar@s
-   for managing this kind of global state.
+   Of course the implementation of this name cache uses @unsavePerformIO@.
+   The global cache is managed by ue of an @IORef@ and atomicModifyIORef.
 
    The following laws hold for atoms
 
@@ -59,11 +59,11 @@
    share                -- :: String -> String
  ) where
 
-import           Control.Concurrent.MVar
 import           Control.DeepSeq
 
 import           Data.ByteString.Internal       ( toForeignPtr, c2w, w2c )
 import           Data.ByteString                ( ByteString, pack, unpack )
+import           Data.IORef
 import qualified Data.Map                       as M
 import           Data.String.UTF8Decoding       ( decodeUtf8 )
 import           Data.String.Unicode            ( unicodeToUtf8 )
@@ -82,8 +82,8 @@
 
 -- | the internal cache for the strings
 
-theAtoms        :: MVar Atoms
-theAtoms        = unsafePerformIO (newMVar M.empty)
+theAtoms        :: IORef Atoms
+theAtoms        = unsafePerformIO (newIORef M.empty)
 {-# NOINLINE theAtoms #-}
 
 -- | insert a bytestring into the atom cache
@@ -103,10 +103,14 @@
 -- | The internal operation running in the IO monad
 newAtom'        :: String -> IO Atom
 newAtom' s      = do
-                  m <- takeMVar theAtoms
-                  let (m', a) = insertAtom (pack. map c2w . unicodeToUtf8 $ s) m
-                  putMVar theAtoms m'
-                  return a
+                  -- putStrLn "insert atom into cache"
+                  res <- atomicModifyIORef theAtoms insert
+                  -- putStrLn "atom cache updated"
+                  return res
+  where
+    insert m    = let r = insertAtom (pack. map c2w . unicodeToUtf8 $ s) m 
+                  in
+                   fst r `seq` r
 
 -- | Insert a @String@ into the atom cache and convert the atom back into a @String@.
 --
diff --git a/src/Text/XML/HXT/DOM/QualifiedName.hs b/src/Text/XML/HXT/DOM/QualifiedName.hs
--- a/src/Text/XML/HXT/DOM/QualifiedName.hs
+++ b/src/Text/XML/HXT/DOM/QualifiedName.hs
@@ -84,13 +84,13 @@
 
 import           Control.Arrow                  ( (***) )
 
-import           Control.Concurrent.MVar
 import           Control.DeepSeq
 import           Control.FlatSeq
 
 import           Data.AssocList
 import           Data.Binary
 import           Data.Char                      ( toLower )
+import           Data.IORef
 import           Data.List                      ( isPrefixOf )
 import qualified Data.Map               as M
 import           Data.Typeable
@@ -354,11 +354,11 @@
 
 mkNsName                          :: String -> String -> QName
 mkNsName n ns
-    | null ns			= qn
-    | otherwise			= setNamespaceUri' ns' qn
+    | null ns                   = qn
+    | otherwise                 = setNamespaceUri' ns' qn
     where
     qn                          = mkName n
-    ns'				= newXName ns
+    ns'                         = newXName ns
 
 -- ------------------------------------------------------------
 
@@ -512,8 +512,8 @@
 
 -- | the internal cache for QNames (and name strings)
 
-theNameCache            :: MVar NameCache
-theNameCache            = unsafePerformIO (newMVar $ initialCache)
+theNameCache            :: IORef NameCache
+theNameCache            = unsafePerformIO (newIORef $ initialCache)
 {-# NOINLINE theNameCache #-}
 
 initialXNames           :: [XName]
@@ -556,14 +556,17 @@
 changeNameCache         :: NFData r => ChangeNameCache r -> r
 changeNameCache action  = unsafePerformIO changeNameCache'
     where
-    changeNameCache'    = do
-                          -- putStrLn "takeMVar"
-                          c <- takeMVar theNameCache
-                          let (c', res) = action c
-                          c' `seq` -- rnf res `seq`
-                             putMVar theNameCache c'
-                          -- putStrLn "putMVar"
-                          return res
+    action' c = 
+      let r = action c 
+      in 
+       fst r `seq` r    -- eval name cache to whnf
+       
+    changeNameCache' = 
+      do
+      -- putStrLn "modify cache"
+      res <- atomicModifyIORef theNameCache action'
+      -- putStrLn "cache modified"
+      return res
 
 {-# NOINLINE changeNameCache #-}
 
@@ -599,7 +602,7 @@
                           newXName' n
 
 newQName                :: XName -> XName -> XName -> QName
-newQName lp px ns       = lp `seq` px `seq` ns `seq`                    -- XNames must be evaluated, else MVar blocks
+newQName lp px ns       = lp `seq` px `seq` ns `seq`            -- XNames must be evaluated, else MVar blocks
                           ( changeNameCache $
                             newQName' lp px ns
                           )