diff --git a/Benchmark.hs b/Benchmark.hs
--- a/Benchmark.hs
+++ b/Benchmark.hs
@@ -2,7 +2,9 @@
 
 import Definitions
 import Shellish hiding ( run )
+import Data.Char
 import Data.List
+import Data.List.Split ( wordsBy )
 import System.Directory
 import System.Environment
 import System.FilePath( (</>), (<.>), splitDirectories, joinPath )
@@ -131,13 +133,18 @@
   resetMemoryUsed
   return $ MemTime (fromIntegral mem) (realToFrac $ diffUTCTime t2 t1)
 
-check_darcs :: String -> IO ()
-check_darcs cmd = do
+darcsVersion :: String -> IO Version
+darcsVersion cmd = do
        (_,outH,_,procH) <- runInteractiveCommand $ cmd ++ " --version"
        out <- strictGetContents outH
        _ <- waitForProcess procH
+       return $ map read . wordsBy (== '.') . takeWhile (not . isSpace) $ out
+
+check_darcs :: String -> IO ()
+check_darcs cmd = do
+       out <- darcsVersion cmd
        case out of
-         '2':'.':_ -> return ()
+         2:_ -> return ()
          _ -> fail $ cmd ++ ": Not darcs 2.x binary."
 
 verbose :: String -> Command ()
@@ -157,6 +164,10 @@
                   _ <- forkIO $ work ""
                   return chan
 
+readFile' :: FilePath -> IO String
+readFile' f = do s <- readFile f
+                 length s `seq` return s
+
 darcs :: String -> [String] -> Command String
 darcs cmd args' = do
     stats_f <- liftIO $
@@ -176,7 +187,7 @@
        res' <- drain outH loud
        errs' <- drain errH loud
        ex <- waitForProcess procH
-       stats <- do c <- readFile stats_f
+       stats <- do c <- readFile' stats_f
                    removeFile stats_f `catch` \e -> hPutStrLn stderr (show e)
                    return c
                 `catch` \_ -> return ""
diff --git a/Definitions.hs b/Definitions.hs
--- a/Definitions.hs
+++ b/Definitions.hs
@@ -29,6 +29,10 @@
                          , pFlush :: Maybe (FilePath -> IO ()) }
 type TimeStamp = UTCTime
 
+type Version = [Int] -- we could also use Data.Version
+                     -- the difference here is just that we explicitly
+                     -- do not have a notion of version tags
+
 global :: IORef (ParamStamp, TimeStamp)
 global = unsafePerformIO $ do t  <- getCurrentTime
                               hn <- getHostName
@@ -139,6 +143,12 @@
 
 allVariants :: [Variant]
 allVariants = map toVariant [minBound .. maxBound]
+
+-- | The subset of variants appropriate to the given darcs version
+appropriateVariants :: Version -> [Variant] -> [Variant]
+appropriateVariants v | v < [2,3,97] = filter ((/= OptimizePristineVariant) . vId)
+                      | v > [2,4,96] = filter ((/= DefaultVariant) . vId)
+                      | otherwise    = id
 
 -- ----------------------------------------------------------------------
 -- long-term storage
diff --git a/Run.hs b/Run.hs
--- a/Run.hs
+++ b/Run.hs
@@ -11,19 +11,22 @@
 
 benchMany :: [TestRepo] -> [TestBinary] -> [Benchmark a] -> Command [(Test a, Maybe MemTimeOutput)]
 benchMany repos bins benches = do
-  fmap concat $ forM (map repoAndVariants repos) $ \rs -> do
+  binsVers <- liftIO $ forM bins $
+    \bin@(TestBinary b) -> do v <- darcsVersion b
+                              return (bin, v)
+  fmap concat $ forM repos $ \r -> do
     res <- sequence
              [ do let test = Test bench repo bin
                   memtime <- run test
                   return (test, memtime)
-               | repo <- rs, bin <- bins, bench <- benches ]
+               | (bin,ver) <- binsVers, repo <- repoAndVariants ver r, bench <- benches ]
     let tables = repoTables benchmarks res
     if length tables == 1 then
       echo_n $ TR.render id id id $ tabulateRepo formatTimeResult (head tables)
       else error "Not expecting more than one table for a repo and its variants"
     return res
  where
-  repoAndVariants r = map (r `tweakVia`) (trVariants r)
+  repoAndVariants v r = map (r `tweakVia`) (appropriateVariants v (trVariants r))
   tweakVia tr v =
    case vId v of
      DefaultVariant -> tr
diff --git a/darcs-benchmark.cabal b/darcs-benchmark.cabal
--- a/darcs-benchmark.cabal
+++ b/darcs-benchmark.cabal
@@ -1,5 +1,5 @@
 name:          darcs-benchmark
-version:       0.1.8.2
+version:       0.1.8.3
 synopsis:      Comparative benchmark suite for darcs.
 
 description: A simple tool to compare performance of different Darcs 2.x
@@ -22,7 +22,8 @@
 executable darcs-benchmark
     if impl(ghc >= 6.8)
       ghc-options: -fwarn-tabs
-    ghc-options:   -Wall -threaded
+
+    ghc-options:   -Wall -threaded -fno-warn-unused-do-bind
     ghc-prof-options: -prof -auto-all -threaded
 
     build-depends: base < 5,