diff --git a/src/client/batch.ml b/src/client/batch.ml
index 600f1b43..005644c2 100644
--- a/src/client/batch.ml
+++ b/src/client/batch.ml
@@ -7,14 +7,15 @@ type 'a t = {
   mutable start: Mtime.t;
 }
 
-let make ?(batch = 1) ?timeout () : _ t =
+let high_watermark batch_size =
+  if batch_size = 1 then
+    100
+  else
+    batch_size * 10
+
+let make ?(batch = 1) ?(high_watermark = high_watermark batch) ?timeout () : _ t
+    =
   assert (batch > 0);
-  let high_watermark =
-    if batch = 1 then
-      100
-    else
-      batch * 10
-  in
   {
     size = 0;
     start = Mtime_clock.now ();
diff --git a/src/client/batch.mli b/src/client/batch.mli
index 37b12857..39fdd4d4 100644
--- a/src/client/batch.mli
+++ b/src/client/batch.mli
@@ -2,15 +2,20 @@
 
 type 'a t
 
-val make : ?batch:int -> ?timeout:Mtime.span -> unit -> 'a t
+val make :
+  ?batch:int -> ?high_watermark:int -> ?timeout:Mtime.span -> unit -> 'a t
 (** [make ()] is a new batch
 
     @param batch
       the number of elements after which the batch will be considered {b full},
-      and ready to pop. A "high water mark" is also derived form the batch as
-      [if batch = 1 then 100 else batch * 10]. This sets a limit after which new
-      elements will be [`Dropped] by {!push}. Set to [0] to disable batching.
-      Default [1].
+      and ready to pop. Set to [0] to disable batching. It is required that
+      [batch >= 0]. Default [1].
+
+    @param high_watermark
+      the batch size limit after which new elements will be [`Dropped] by
+      {!push}. This prevents the queue from growing too fast for effective
+      transmission in case of signal floods. Default
+      [if batch = 1 then 100 else batch * 10].
 
     @param timeout
       the time span after which a batch is ready to pop, whether or not it is