diff --git a/creatur.cabal b/creatur.cabal
--- a/creatur.cabal
+++ b/creatur.cabal
@@ -1,5 +1,5 @@
 Name:              creatur
-Version:           5.7.1
+Version:           5.7.2
 Stability:         experimental
 Synopsis:          Framework for artificial life experiments.
 Description:       A software framework for automating experiments
@@ -36,7 +36,7 @@
 source-repository this
   type:     git
   location: https://github.com/mhwombat/creatur.git
-  tag:      5.7.1
+  tag:      5.7.2
 
 library
   GHC-Options:      -Wall -fno-warn-orphans
diff --git a/src/ALife/Creatur/Persistent.hs b/src/ALife/Creatur/Persistent.hs
--- a/src/ALife/Creatur/Persistent.hs
+++ b/src/ALife/Creatur/Persistent.hs
@@ -32,7 +32,7 @@
     psValue :: a,
     psDefaultValue :: a,
     psFilename :: FilePath
-  } deriving (Show, Eq)
+  } deriving (Show, Read, Eq)
 
 -- | Creates a counter that will store its value in the specified file.
 mkPersistent :: a -> FilePath -> Persistent a