diff --git a/safecopy.cabal b/safecopy.cabal
--- a/safecopy.cabal
+++ b/safecopy.cabal
@@ -3,7 +3,7 @@
 -- http://www.haskell.org/cabal/release/cabal-latest/doc/users-guide/authors.html#pkg-descr.
 -- The name of the package.
 Name:                safecopy
-Version:             0.9.3.1
+Version:             0.9.3.2
 Synopsis:            Binary serialization with version control.
 Description:         An extension to Data.Serialize with built-in version control.
 Homepage:            https://github.com/acid-state/safecopy
diff --git a/src/Data/SafeCopy/Derive.hs b/src/Data/SafeCopy/Derive.hs
--- a/src/Data/SafeCopy/Derive.hs
+++ b/src/Data/SafeCopy/Derive.hs
@@ -350,7 +350,7 @@
     where
       manyConstructors = length cons > 1 || forceTag deriveType
       mkPutClause (conNumber, con)
-          = do putVars <- replicateM (conSize con) (newName "arg")
+          = do putVars <- mapM (\n -> newName ("a" ++ show n)) [1..conSize con]
                (putFunsDecs, putFuns) <- case deriveType of
                                            Normal -> mkSafeFunctions "safePut_" 'getSafePut con
                                            _      -> return ([], const 'safePut)
diff --git a/src/Data/SafeCopy/SafeCopy.hs b/src/Data/SafeCopy/SafeCopy.hs
--- a/src/Data/SafeCopy/SafeCopy.hs
+++ b/src/Data/SafeCopy/SafeCopy.hs
@@ -122,7 +122,7 @@
     -- message strings.
     -- Feel free to leave undefined in your instances.
     errorTypeName :: Proxy a -> String
-    errorTypeName _ = "<unkown type>"
+    errorTypeName _ = "<unknown type>"
 
 #ifdef DEFAULT_SIGNATURES
     default getCopy :: Serialize a => Contained (Get a)