diff --git a/Makefile b/Makefile
index 98ac4679..dbe3780d 100644
--- a/Makefile
+++ b/Makefile
@@ -21,10 +21,11 @@ DUNE_OPTS_BENCH?=--profile=release
 N?=40
 NITER?=3
 BENCH_PSIZE?=1,4,8,20
+BENCH_CUTOFF?=20
 bench-fib:
 	@echo running for N=$(N)
 	dune build $(DUNE_OPTS_BENCH) benchs/fib_rec.exe
 	hyperfine -L psize $(BENCH_PSIZE) \
-		'./_build/default/benchs/fib_rec.exe -niter $(NITER) -psize={psize} -n $(N)'
+		'./_build/default/benchs/fib_rec.exe -cutoff $(BENCH_CUTOFF) -niter $(NITER) -psize={psize} -n $(N)'
 
 .PHONY: test clean
diff --git a/benchs/fib_rec.ml b/benchs/fib_rec.ml
index 36d8c704..4ff984f4 100644
--- a/benchs/fib_rec.ml
+++ b/benchs/fib_rec.ml
@@ -6,8 +6,10 @@ let rec fib_direct x =
   else
     fib_direct (x - 1) + fib_direct (x - 2)
 
+let cutoff = ref 20
+
 let rec fib ~on x : int Fut.t =
-  if x <= 20 then
+  if x <= !cutoff then
     Fut.spawn ~on (fun () -> fib_direct x)
   else
     let open Fut.Infix_local in
@@ -42,6 +44,7 @@ let () =
       "-n", Arg.Set_int n, " fib <n>";
       "-seq", Arg.Set seq, " sequential";
       "-niter", Arg.Set_int niter, " number of iterations";
+      "-cutoff", Arg.Set_int cutoff, " cutoff for sequential computation";
     ]
     |> Arg.align
   in