diff --git a/unix-process-conduit.cabal b/unix-process-conduit.cabal
--- a/unix-process-conduit.cabal
+++ b/unix-process-conduit.cabal
@@ -2,7 +2,7 @@
 --  documentation, see http://haskell.org/cabal/users-guide/
 
 name:                unix-process-conduit
-version:             0.2.1
+version:             0.2.1.1
 synopsis:            Run processes on Unix systems, with a conduit interface
 description:         This library allows you to provide @conduit@ datatypes for the input and output streams. Note that you must compile your programs with @-threaded@.
 homepage:            https://github.com/snoyberg/conduit
@@ -25,7 +25,7 @@
                      , process           >= 1.1
                      , time
                      , filepath
-                     , stm
+                     , stm               >= 2.4
                      , directory
   c-sources:           cbits/process-tracker.c