diff --git a/src/lang/lang_builtins.ml b/src/lang/lang_builtins.ml
index 6380d3a42b..efdaa88752 100644
--- a/src/lang/lang_builtins.ml
+++ b/src/lang/lang_builtins.ml
@@ -1747,7 +1747,7 @@ let () =
              in
              (timed_out, !status))
        in
-       on_done (if 0. <= timeout then asynchronous() else synchronous ()))      
+       on_done (if 0. <= timeout && Tutils.has_started() then asynchronous() else synchronous ()))      
 
 let () =
   let ret_t = Lang.list_t (Lang.product_t Lang.string_t Lang.string_t) in
diff --git a/src/tools/tutils.ml b/src/tools/tutils.ml
index 8d4639363c..fd94ea99d9 100644
--- a/src/tools/tutils.ml
+++ b/src/tools/tutils.ml
@@ -182,6 +182,13 @@ type priority =
 
 let scheduler = Duppy.create ()
 
+let started  = ref false
+
+let started_m = Mutex.create ()
+
+let has_started = mutexify started_m (fun () ->
+  !started)
+
 let () =
   let name = "Duppy scheduler shutdown" in
   let f () =
@@ -239,7 +246,9 @@ let () =
           new_queue
             ~priorities:(fun x -> x = Non_blocking)
             ~name ()
-        done))
+        done;
+      mutexify started_m (fun () ->
+        started := true) ()))
 
 (** Replace stdout/err by a pipe, and install a Duppy task that pulls data
   * out of that pipe and logs it.
diff --git a/src/tools/tutils.mli b/src/tools/tutils.mli
index 97c66c0adf..ec6a87091c 100644
--- a/src/tools/tutils.mli
+++ b/src/tools/tutils.mli
@@ -31,6 +31,7 @@
   raises an exception. *)
 val create : ('a -> unit) -> 'a -> string -> Thread.t
 val main : unit -> unit
+val has_started : unit -> bool
 val shutdown : unit -> unit
 
 (** Special exception allowed for "clean" termination of Tutils threads.