diff --git a/lib/js_of_ocaml/js.ml b/lib/js_of_ocaml/js.ml
index 3349b04ec..481622854 100644
--- a/lib/js_of_ocaml/js.ml
+++ b/lib/js_of_ocaml/js.ml
@@ -838,9 +838,12 @@ let export_js (field : js_string t) x =
   Unsafe.set
     (Unsafe.pure_js_expr "jsoo_exports")
     field
-    (if String.equal (Js.to_string (typeof (Obj.magic x))) "function"
-        (* function with arity/length equal to zero are already wrapped *)
-        && Unsafe.get (Obj.magic x) (Js.string "length") > 0
+    (if match Sys.backend_type with
+        | Other "wasm_of_ocaml" -> Obj.tag (Obj.repr x) = Obj.closure_tag
+        | _ ->
+            String.equal (Js.to_string (typeof (Obj.magic x))) "function"
+            (* function with arity/length equal to zero are already wrapped *)
+            && Unsafe.get (Obj.magic x) (Js.string "length") > 0
      then Obj.magic (wrap_callback (Obj.magic x))
      else x)
 
diff --git a/lib/tests/test_fun_call.ml b/lib/tests/test_fun_call.ml
index 70c109851..f36b0b871 100644
--- a/lib/tests/test_fun_call.ml
+++ b/lib/tests/test_fun_call.ml
@@ -409,16 +409,14 @@ let%expect_test _ =
   [%expect {|
     Result: other |}]
 
-(*ZZZ
-  let%expect_test _ =
-    let open Js_of_ocaml in
-    let f = Js.wrap_callback (fun s -> print_endline s) in
-    Js.export "f" f;
-    let () =
-      Js.Unsafe.fun_call
-        (Js.Unsafe.pure_js_expr "jsoo_exports")##.f
-        [| Js.Unsafe.coerce (Js.string "hello") |]
-    in
-    ();
-    [%expect {| hello |}]
-*)
+let%expect_test _ =
+  let open Js_of_ocaml in
+  let f = Js.wrap_callback (fun s -> print_endline (Js.to_string s)) in
+  Js.export "f" f;
+  let () =
+    Js.Unsafe.fun_call
+      (Js.Unsafe.pure_js_expr "jsoo_exports")##.f
+      [| Js.Unsafe.coerce (Js.string "hello") |]
+  in
+  ();
+  [%expect {| hello |}]
diff --git a/runtime/wasm/runtime.js b/runtime/wasm/runtime.js
index ed8a609ec..31ba054a3 100644
--- a/runtime/wasm/runtime.js
+++ b/runtime/wasm/runtime.js
@@ -376,5 +376,5 @@
             event.error&&caml_handle_uncaught_exception(event.error))
     }
     await _initialize();
-})(((joo_global_object,globalThis)=>(x)=>eval(x))(globalThis,globalThis),
+})(((joo_global_object,jsoo_exports,globalThis)=>(x)=>eval(x))(globalThis,globalThis?.module?.exports||globalThis,globalThis),
    PRIMITIVES);