diff --git a/CHANGES.md b/CHANGES.md
index 2cbae0c613..fd6bd8f8a8 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -14,6 +14,7 @@
 * Runtime/wasm: fix Unix.times (#2096)
 * Ppx: disable spurious warning for unused "self" in object litteral (#2128)
 * Ppx: fix labelled arguments for methods (#2126)
+* Runtime: runtime with target-env=browser should not rely on "require(..)" (#2129)
 
 # 6.2.0 (2025-07-30) - Lille
 
diff --git a/compiler/tests-compiler/target_env.ml b/compiler/tests-compiler/target_env.ml
index 70144741ad..8b17a16f1e 100644
--- a/compiler/tests-compiler/target_env.ml
+++ b/compiler/tests-compiler/target_env.ml
@@ -61,3 +61,46 @@ let () =
     without node filesystem
     Sys.readdir ok
     empty root |}]
+
+module Jsoo = Js_of_ocaml_compiler
+module StringSet = Set.Make (String)
+
+class find_require r =
+  object
+    inherit Jsoo.Js_traverse.iter as super
+
+    method! expression e =
+      (match e with
+      | ECall (EVar (Jsoo.Javascript.S { name = Utf8 "require"; loc; _ }), _, args, _)
+        -> (
+          match args with
+          | [ Arg name ] -> (
+              match name with
+              | EStr (Utf8 name) -> r := (name, loc) :: !r
+              | _ -> r := ("<Unknown>", loc) :: !r)
+          | _ -> assert false)
+      | _ -> ());
+      super#expression e
+  end
+
+(* Check target-env=browser doesn't use 'require("node:...")' *)
+let%expect_test _ =
+  let test flags =
+    let r = ref [] in
+    let o = new find_require r in
+    let p = compile_and_parse_whole_program ~flags "" in
+    o#program p;
+    let ss =
+      List.fold_left
+        (fun acc (x, _loc) ->
+          let x = if String.starts_with ~prefix:"node:" x then "node" else x in
+          StringSet.add x acc)
+        StringSet.empty
+        !r
+    in
+    StringSet.iter (fun name -> Printf.eprintf "%s\n" name) ss
+  in
+  test [ "--linkall" ];
+  [%expect {| node |}];
+  test [ "--linkall"; "--target-env=browser" ];
+  [%expect {| |}]
diff --git a/runtime/js/sys.js b/runtime/js/sys.js
index 98a9ed5001..e43c3974a0 100644
--- a/runtime/js/sys.js
+++ b/runtime/js/sys.js
@@ -384,6 +384,14 @@ function caml_sys_temp_dir_name(_unit) {
   }
 }
 
+//Provides: caml_sys_temp_dir_name
+//Requires: caml_string_of_jsstring
+//Version: >= 5.4
+//If: browser
+function caml_sys_temp_dir_name(_unit) {
+  return caml_string_of_jsstring("");
+}
+
 //Provides: caml_sys_convert_signal_number
 //Version: >= 5.4
 function caml_sys_convert_signal_number(signo) {
diff --git a/runtime/js/unix.js b/runtime/js/unix.js
index 953b2ad0d4..146042617b 100644
--- a/runtime/js/unix.js
+++ b/runtime/js/unix.js
@@ -228,6 +228,14 @@ function caml_strerror(errno) {
   }
 }
 
+//Provides: caml_strerror
+//Requires: unix_error
+//If: browser
+function caml_strerror(errno) {
+  const code = unix_error[errno];
+  code || "Unknown error " + errno;
+}
+
 //Provides: unix_error_message
 //Alias: caml_unix_error_message
 //Requires: caml_strerror, caml_string_of_jsstring