diff --git a/CHANGELOG.markdown b/CHANGELOG.markdown
--- a/CHANGELOG.markdown
+++ b/CHANGELOG.markdown
@@ -7,6 +7,24 @@
 *de facto* standard Haskell versioning scheme.
 
 
+1.2.1.2
+-------
+
+- **Date**    2017-10-14
+- **Git tag** [concurrency-1.2.1.2][]
+- **Hackage** https://hackage.haskell.org/package/concurrency-1.2.1.2
+
+### Control.Monad.Conc.Class
+
+- Fixes an infinite loop introduced for the `IO` instance of `MonadConc` in `forkWithUnmask` and
+  `forkOnWithUnmask` in 1.2.1.1 (#134).
+
+[concurrency-1.2.1.2]: https://github.com/barrucadu/dejafu/releases/tag/concurrency-1.2.1.2
+
+
+---------------------------------------------------------------------------------------------------
+
+
 1.2.1.1
 -------
 
diff --git a/Control/Monad/Conc/Class.hs b/Control/Monad/Conc/Class.hs
--- a/Control/Monad/Conc/Class.hs
+++ b/Control/Monad/Conc/Class.hs
@@ -614,6 +614,9 @@
   fork   = IO.forkIO
   forkOn = IO.forkOn
 
+  forkWithUnmask   = IO.forkIOWithUnmask
+  forkOnWithUnmask = IO.forkOnWithUnmask
+
   forkWithUnmaskN n ma = forkWithUnmask $ \umask -> do
     labelMe n
     ma umask
diff --git a/concurrency.cabal b/concurrency.cabal
--- a/concurrency.cabal
+++ b/concurrency.cabal
@@ -2,7 +2,7 @@
 -- documentation, see http://haskell.org/cabal/users-guide/
 
 name:                concurrency
-version:             1.2.1.1
+version:             1.2.1.2
 synopsis:            Typeclasses, functions, and data types for concurrency and STM.
 
 description:
@@ -32,7 +32,7 @@
 source-repository this
   type:     git
   location: https://github.com/barrucadu/dejafu.git
-  tag:      concurrency-1.2.1.1
+  tag:      concurrency-1.2.1.2
 
 library
   exposed-modules:     Control.Monad.Conc.Class