diff --git a/CHANGELOG.rst b/CHANGELOG.rst
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -6,6 +6,18 @@
 
 .. _PVP: https://pvp.haskell.org/
 
+2.3.0.0 (2020-05-14)
+--------------------
+
+* Git: :tag:`dejafu-2.3.0.0`
+* Hackage: :hackage:`dejafu-2.3.0.0`
+
+Miscellaneous
+~~~~~~~~~~~~~
+
+* The version bound on :hackage:`concurrency` is >=1.11 <1.12.
+
+
 2.2.0.0 (2020-05-10)
 --------------------
 
diff --git a/Test/DejaFu/Conc/Internal/Program.hs b/Test/DejaFu/Conc/Internal/Program.hs
--- a/Test/DejaFu/Conc/Internal/Program.hs
+++ b/Test/DejaFu/Conc/Internal/Program.hs
@@ -141,6 +141,8 @@
 
   getMaskingState = ModelConc (\c -> AGetMasking c)
 
+  unsafeUnmask ma = ModelConc (AMasking Unmasked (const ma))
+
   -- ----------
 
   atomically = ModelConc . AAtom
diff --git a/dejafu.cabal b/dejafu.cabal
--- a/dejafu.cabal
+++ b/dejafu.cabal
@@ -2,7 +2,7 @@
 -- documentation, see http://haskell.org/cabal/users-guide/
 
 name:                dejafu
-version:             2.2.0.0
+version:             2.3.0.0
 synopsis:            A library for unit-testing concurrent programs.
 
 description:
@@ -20,7 +20,7 @@
 license-file:        LICENSE
 author:              Michael Walker
 maintainer:          mike@barrucadu.co.uk
-copyright:           (c) 2015--2019 Michael Walker
+copyright:           (c) 2015--2020 Michael Walker
 category:            Concurrency
 build-type:          Simple
 extra-source-files:  README.markdown CHANGELOG.rst
@@ -33,7 +33,7 @@
 source-repository this
   type:     git
   location: https://github.com/barrucadu/dejafu.git
-  tag:      dejafu-2.2.0.0
+  tag:      dejafu-2.3.0.0
 
 library
   exposed-modules:     Test.DejaFu
@@ -59,7 +59,7 @@
   -- other-modules:       
   -- other-extensions:    
   build-depends:       base              >=4.9 && <5
-                     , concurrency       >=1.10 && <1.11
+                     , concurrency       >=1.11 && <1.12
                      , containers        >=0.5 && <0.7
                      , contravariant     >=1.2 && <1.6
                      , deepseq           >=1.1 && <2
