diff --git a/CHANGES.md b/CHANGES.md
index 41dde46b9b..356d6d52b4 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -79,6 +79,7 @@ Changed:
 - Added `settings.protocol.youtube_dl.timeout` to specify timeout when using
   `youtube-dl` protocol (#2827). Use `yt-dlp` as default binary for the
   protocol.
+- The `sleeper` operator is now scripted (#2899).
 
 Fixed:
 
diff --git a/src/core/dune b/src/core/dune
index bd0a3d3599..5133c8f385 100644
--- a/src/core/dune
+++ b/src/core/dune
@@ -216,7 +216,6 @@
   sha1
   shebang
   shine_format
-  sleeper
   source
   speex_format
   srt_decoder
diff --git a/src/core/operators/sleeper.ml b/src/core/operators/sleeper.ml
deleted file mode 100644
index 59c5254822..0000000000
--- a/src/core/operators/sleeper.ml
+++ /dev/null
@@ -1,87 +0,0 @@
-(*****************************************************************************
-
-  Liquidsoap, a programmable audio stream generator.
-  Copyright 2003-2023 Savonet team
-
-  This program is free software; you can redistribute it and/or modify
-  it under the terms of the GNU General Public License as published by
-  the Free Software Foundation; either version 2 of the License, or
-  (at your option) any later version.
-
-  This program is distributed in the hope that it will be useful,
-  but WITHOUT ANY WARRANTY; without even the implied warranty of
-  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-  GNU General Public License for more details, fully stated in the COPYING
-  file at the root of the liquidsoap distribution.
-
-  You should have received a copy of the GNU General Public License
-  along with this program; if not, write to the Free Software
-  Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301  USA
-
- *****************************************************************************)
-
-open Source
-
-class sleeper source delay random =
-  let dt = AFrame.duration () in
-  object
-    inherit operator [source]
-    val mutable lived = 0.
-    method stype = source#stype
-    method remaining = source#remaining
-    method seek = source#seek
-    method is_ready = source#is_ready
-    method abort_track = source#abort_track
-    method self_sync = source#self_sync
-    val mutable freeze = false
-    method freeze = freeze <- true
-
-    method private get_frame buf =
-      source#get buf;
-      let delay = delay +. Random.float random in
-      Thread.delay delay;
-      lived <- lived +. max dt delay;
-      if freeze then
-        while true do
-          Thread.delay 60.
-        done
-  end
-
-let _ =
-  let freeze s =
-    Lang.val_fun [] (fun _ ->
-        s#freeze;
-        Lang.unit)
-  in
-  let frame_t = Lang.frame_t (Lang.univ_t ()) Frame.Fields.empty in
-  Lang.add_operator "sleeper"
-    [
-      ( "delay",
-        Lang.float_t,
-        Some (Lang.float 1.),
-        Some
-          "Amount of time to sleep, in seconds per second of produced audio \
-           data." );
-      ( "random",
-        Lang.float_t,
-        Some (Lang.float 0.),
-        Some "Maximal amount of time randomly added to the delay parameter." );
-      ("", Lang.source_t frame_t, None, None);
-    ]
-    ~return_t:frame_t
-    ~descr:"Sleep at each frame. Useful for emulating network delays, etc."
-    ~category:`Testing ~flags:[`Experimental]
-    ~meth:
-      [
-        ( "freeze",
-          ([], Lang.fun_t [] Lang.unit_t),
-          "Freeze the main thread.",
-          freeze );
-      ]
-    (fun p ->
-      let delay = Lang.to_float (List.assoc "delay" p) in
-      let delay = AFrame.duration () *. delay in
-      let random = Lang.to_float (List.assoc "random" p) in
-      let random = AFrame.duration () *. random in
-      let src = Lang.to_source (List.assoc "" p) in
-      new sleeper src delay random)
diff --git a/src/libs/stdlib.liq b/src/libs/stdlib.liq
index 5979f1b4e7..ef44250190 100644
--- a/src/libs/stdlib.liq
+++ b/src/libs/stdlib.liq
@@ -42,6 +42,7 @@
 %include "profiler.liq"
 %include "io.liq"
 %include "runtime.liq"
+%include "testing.liq"
 %include "liquidsoap.liq"
 
 set_settings_ref(settings)
diff --git a/src/libs/testing.liq b/src/libs/testing.liq
new file mode 100644
index 0000000000..c0fec6d013
--- /dev/null
+++ b/src/libs/testing.liq
@@ -0,0 +1,24 @@
+# Sleep regularly, thus inducing delays in the sound production. This is mainly
+# useful for emulating network delays or sources which are slow to produce data,
+# and thus test bufferization and robustness of scripts.
+# @category Source / Testing
+# @flag experimental
+# @param ~every How often we should sleep (in seconds, 0 means every frame).
+# @param ~delay Delay introduced (in seconds).
+# @param ~delay_random Maximum amount of time randomly added to the delay (in seconds).
+# @param s Source in which the delays should be introduced.
+# @method frozen The stream production is frozen while set to `true`.
+def sleeper(~every=0.5, ~delay=0.1, ~delay_random=0., s)
+  last = ref(0.)
+  frozen = ref(false)
+  def f()
+    now = source.time(s)
+    while frozen() do sleep(0.1) end
+    if now + every >= last() then
+      last := now
+      sleep(delay + random.float(max=delay_random))
+    end
+  end
+  s = source.on_frame(s,f)
+  s.{frozen = frozen}
+end