diff --git a/CHANGES b/CHANGES
--- a/CHANGES
+++ b/CHANGES
@@ -1,3 +1,9 @@
+= Version 1.2.0.1, 2011-09-21 =
+* Add missing StandaloneDeriving and DeriveDataTypeable
+GHC extensions to enable Typeable deriving. Also remove
+PatternGuards extension, which was needed only once.
+
+
 = Version 1.2.0.0, 2011-05-08 =
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 * Rename HashMap and HashSet to Map and Set.
diff --git a/Data/HashMap.hs b/Data/HashMap.hs
--- a/Data/HashMap.hs
+++ b/Data/HashMap.hs
@@ -1,5 +1,3 @@
-{-# LANGUAGE CPP, PatternGuards #-}
-
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Data.HashMap
@@ -572,8 +570,9 @@
 isSubmapOfBy f (Map m1) (Map m2) =
   I.isSubmapOfBy some_isSubmapOfBy m1 m2
   where some_isSubmapOfBy (Only k x) (Only l y) = k `eq` l && x `f` y
-        some_isSubmapOfBy (Only k x) (More t) | Just y <- M.lookup k t = f x y
-                                              | otherwise              = False
+        some_isSubmapOfBy (Only k x) (More t) = case M.lookup k t of
+                                                  Just y -> f x y
+                                                  _      -> False
         some_isSubmapOfBy (More _) (Only _ _) = False
         some_isSubmapOfBy (More t) (More u)   = M.isSubmapOfBy f t u
 
diff --git a/Data/HashSet.hs b/Data/HashSet.hs
--- a/Data/HashSet.hs
+++ b/Data/HashSet.hs
@@ -1,6 +1,3 @@
-{-# LANGUAGE CPP #-}
-{-# OPTIONS -Wall #-}
-
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  Data.HashSet
diff --git a/hashmap.cabal b/hashmap.cabal
--- a/hashmap.cabal
+++ b/hashmap.cabal
@@ -1,5 +1,5 @@
 Name:                hashmap
-Version:             1.2.0.0
+Version:             1.2.0.1
 Synopsis:            Persistent containers Map and Set based on hashing.
 Description:         An implementation of persistent 'Map' and 'Set' containers
                      based on hashing. The implementation is build on
@@ -25,7 +25,7 @@
 Stability:           Provisional
 Category:            Data
 Build-type:          Simple
-Cabal-version:       >= 1.2
+Cabal-version:       >= 1.6
 Extra-source-files:  CHANGES
 
 Library
@@ -34,3 +34,7 @@
   Build-depends:     base >= 4.0 && < 5,
                      containers >= 0.3,
                      hashable >= 1.0
+
+  Extensions:        CPP
+  if impl(ghc)
+    Extensions:      StandaloneDeriving, DeriveDataTypeable