diff --git a/dejafu/Test/DejaFu/Conc.hs b/dejafu/Test/DejaFu/Conc.hs
index 16a72b3..4b95e37 100755
--- a/dejafu/Test/DejaFu/Conc.hs
+++ b/dejafu/Test/DejaFu/Conc.hs
@@ -177,7 +177,7 @@ runConcurrent :: MonadRef r n
               -> Conc n r a
               -> n (Either Failure a, s, Trace)
 runConcurrent sched memtype s ma = do
-  (res, s', trace) <- runConcurrency sched memtype s (unC ma)
+  (res, s', trace) <- runConcurrency sched memtype s 2 (unC ma)
   pure (res, s', F.toList trace)
 
 -- | Run a concurrent computation and return its result.
diff --git a/dejafu/Test/DejaFu/Conc/Internal.hs b/dejafu/Test/DejaFu/Conc/Internal.hs
index 3652fa3..b230b10 100755
--- a/dejafu/Test/DejaFu/Conc/Internal.hs
+++ b/dejafu/Test/DejaFu/Conc/Internal.hs
@@ -51,14 +51,15 @@ runConcurrency :: MonadRef r n
                => Scheduler g
                -> MemType
                -> g
+               -> Int
                -> M n r a
                -> n (Either Failure a, g, SeqTrace)
-runConcurrency sched memtype g ma = do
+runConcurrency sched memtype g caps ma = do
   ref <- newRef Nothing
 
   let c = runCont ma (AStop . writeRef ref . Just . Right)
   let threads = launch' Unmasked initialThread (const c) M.empty
-  let ctx = Context { cSchedState = g, cIdSource = initialIdSource, cThreads = threads, cWriteBuf = emptyBuffer, cCaps = 2 }
+  let ctx = Context { cSchedState = g, cIdSource = initialIdSource, cThreads = threads, cWriteBuf = emptyBuffer, cCaps = caps }
 
   (finalCtx, trace) <- runThreads sched memtype ref ctx
   out <- readRef ref
@@ -360,7 +361,7 @@ stepThread sched memtype tid action ctx = case action of
     ASub ma c
       | M.size (cThreads ctx) > 1 -> pure (Left IllegalSubconcurrency)
       | otherwise -> do
-          (res, g', trace) <- runConcurrency sched memtype (cSchedState ctx) ma
+          (res, g', trace) <- runConcurrency sched memtype (cSchedState ctx) (cCaps ctx) ma
           pure $ Right (ctx { cThreads = goto (c res) tid (cThreads ctx), cSchedState = g' }, Left (Subconcurrency, trace))
   where