diff --git a/CHANGELOG.md b/CHANGELOG.md
index 01a231c23d..3a0834c43c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -19,8 +19,8 @@
 #### :bug: Bug Fix
 
 - Improve error when using '@deriving(accessors)' on a variant with record arguments. https://github.com/rescript-lang/rescript-compiler/pull/6712
-
 - Stop escaping JSX prop names with hyphens. https://github.com/rescript-lang/rescript-compiler/pull/6705
+- Fix trailing undefined for optional parameters not omitted with `@send` and `@new`. https://github.com/rescript-lang/rescript-compiler/pull/6716
 
 # 11.1.0-rc.7
 
diff --git a/jscomp/core/lam_compile_external_call.ml b/jscomp/core/lam_compile_external_call.ml
index 9a7a92190e..77a982ccd1 100644
--- a/jscomp/core/lam_compile_external_call.ml
+++ b/jscomp/core/lam_compile_external_call.ml
@@ -151,6 +151,27 @@ type specs = External_arg_spec.params
 
 type exprs = E.t list
 
+let keep_non_undefined_args (arg_types : specs) (args : exprs) =
+  let rec has_undefined_trailing_args arg_types args =
+    match (arg_types, args) with
+    | ( [{External_arg_spec.arg_label = Arg_optional; _}],
+        [{J.expression_desc = Undefined {isUnit = false}; _}] ) ->
+      true
+    | ( _ :: arg_types_rest, _ :: args_rest ) ->
+      has_undefined_trailing_args arg_types_rest args_rest
+    | _ -> false
+  in
+  let rec aux arg_types args =
+    match (arg_types, args) with
+    | ( {External_arg_spec.arg_label = Arg_optional; _} :: arg_types_rest,
+        {J.expression_desc = Undefined {isUnit = false}; _} :: args_rest ) ->
+          aux arg_types_rest args_rest
+    | _ -> args
+  in
+  if (has_undefined_trailing_args arg_types args) then 
+    aux (List.rev arg_types) (List.rev args) |> List.rev
+  else args 
+
 (* TODO: fix splice,
    we need a static guarantee that it is static array construct
    otherwise, we should provide a good error message here,
@@ -176,7 +197,7 @@ let assemble_args_no_splice (arg_types : specs) (args : exprs) :
     | _ :: _, [] -> assert false
   in
   let args, eff = aux arg_types args in
-  ( args,
+  ( keep_non_undefined_args arg_types args,
     match eff with
     | [] -> None
     | x :: xs ->
@@ -271,16 +292,6 @@ let translate_ffi (cxt : Lam_compile_context.t) arg_types
           else E.call ~info:{ arity = Full; call_info = Call_na } fn args)
       else
         let args, eff = assemble_args_no_splice arg_types args in
-        let rec keepNonUndefinedArgs argsList (argTypes : specs) =
-          match (argsList, argTypes) with
-          | ( {J.expression_desc = Undefined {isUnit = false}; _} :: rest,
-              {External_arg_spec.arg_label = Arg_optional; _} :: argTypes ) ->
-            keepNonUndefinedArgs rest argTypes
-          | _ -> argsList
-        in
-        let args =
-          keepNonUndefinedArgs (List.rev args) (List.rev arg_types) |> List.rev
-        in
         add_eff eff
         @@ E.call ~info:{ arity = Full; call_info = Call_na } fn args
   | Js_module_as_fn { external_module_name; splice } ->
diff --git a/jscomp/runtime/release.ninja b/jscomp/runtime/release.ninja
index 317583d49c..d21ca55b4d 100644
--- a/jscomp/runtime/release.ninja
+++ b/jscomp/runtime/release.ninja
@@ -25,7 +25,7 @@ o runtime/caml_exceptions.cmj : cc_cmi runtime/caml_exceptions.res | runtime/cam
 o runtime/caml_exceptions.cmi : cc runtime/caml_exceptions.resi | runtime/bs_stdlib_mini.cmi runtime/js.cmi runtime/js.cmj
 o runtime/caml_float.cmj : cc_cmi runtime/caml_float.res | runtime/caml_float.cmi runtime/caml_float_extern.cmj
 o runtime/caml_float.cmi : cc runtime/caml_float.resi | runtime/bs_stdlib_mini.cmi runtime/js.cmi runtime/js.cmj
-o runtime/caml_format.cmj : cc_cmi runtime/caml_format.ml | runtime/caml_float.cmj runtime/caml_float_extern.cmj runtime/caml_format.cmi runtime/caml_int64.cmj runtime/caml_int64_extern.cmj runtime/caml_nativeint_extern.cmj runtime/caml_string_extern.cmj
+o runtime/caml_format.cmj : cc_cmi runtime/caml_format.ml | runtime/caml.cmj runtime/caml_float.cmj runtime/caml_float_extern.cmj runtime/caml_format.cmi runtime/caml_int64.cmj runtime/caml_int64_extern.cmj runtime/caml_nativeint_extern.cmj runtime/caml_string_extern.cmj
 o runtime/caml_format.cmi : cc runtime/caml_format.mli | runtime/bs_stdlib_mini.cmi runtime/js.cmi runtime/js.cmj
 o runtime/caml_hash.cmj : cc_cmi runtime/caml_hash.res | runtime/caml_hash.cmi runtime/caml_hash_primitive.cmj runtime/caml_nativeint_extern.cmj runtime/js.cmj
 o runtime/caml_hash.cmi : cc runtime/caml_hash.resi | runtime/bs_stdlib_mini.cmi runtime/js.cmi runtime/js.cmj
@@ -41,7 +41,7 @@ o runtime/caml_md5.cmj : cc_cmi runtime/caml_md5.res | runtime/caml_array_extern
 o runtime/caml_md5.cmi : cc runtime/caml_md5.resi | runtime/bs_stdlib_mini.cmi runtime/js.cmi runtime/js.cmj
 o runtime/caml_module.cmj : cc_cmi runtime/caml_module.res | runtime/caml_array_extern.cmj runtime/caml_module.cmi runtime/caml_obj.cmj
 o runtime/caml_module.cmi : cc runtime/caml_module.resi | runtime/bs_stdlib_mini.cmi runtime/js.cmi runtime/js.cmj
-o runtime/caml_obj.cmj : cc_cmi runtime/caml_obj.res | runtime/caml_array_extern.cmj runtime/caml_obj.cmi runtime/caml_option.cmj runtime/js.cmj
+o runtime/caml_obj.cmj : cc_cmi runtime/caml_obj.res | runtime/caml.cmj runtime/caml_array_extern.cmj runtime/caml_obj.cmi runtime/caml_option.cmj runtime/js.cmj
 o runtime/caml_obj.cmi : cc runtime/caml_obj.resi | runtime/bs_stdlib_mini.cmi runtime/js.cmi runtime/js.cmj
 o runtime/caml_option.cmj : cc_cmi runtime/caml_option.res | runtime/caml_option.cmi runtime/caml_undefined_extern.cmj runtime/js.cmj
 o runtime/caml_option.cmi : cc runtime/caml_option.resi | runtime/bs_stdlib_mini.cmi runtime/caml_undefined_extern.cmj runtime/js.cmi runtime/js.cmj
@@ -58,7 +58,7 @@ o runtime/caml_bigint_extern.cmi runtime/caml_bigint_extern.cmj : cc runtime/cam
 o runtime/caml_external_polyfill.cmi runtime/caml_external_polyfill.cmj : cc runtime/caml_external_polyfill.res | runtime/bs_stdlib_mini.cmi runtime/js.cmi runtime/js.cmj
 o runtime/caml_float_extern.cmi runtime/caml_float_extern.cmj : cc runtime/caml_float_extern.res | runtime/bs_stdlib_mini.cmi runtime/js.cmi runtime/js.cmj
 o runtime/caml_int64_extern.cmi runtime/caml_int64_extern.cmj : cc runtime/caml_int64_extern.res | runtime/bs_stdlib_mini.cmi runtime/js.cmi runtime/js.cmj
-o runtime/caml_js_exceptions.cmi runtime/caml_js_exceptions.cmj : cc runtime/caml_js_exceptions.res | runtime/bs_stdlib_mini.cmi runtime/caml_exceptions.cmj runtime/js.cmi runtime/js.cmj
+o runtime/caml_js_exceptions.cmi runtime/caml_js_exceptions.cmj : cc runtime/caml_js_exceptions.res | runtime/bs_stdlib_mini.cmi runtime/caml_exceptions.cmj runtime/caml_option.cmj runtime/js.cmi runtime/js.cmj
 o runtime/caml_nativeint_extern.cmi runtime/caml_nativeint_extern.cmj : cc runtime/caml_nativeint_extern.res | runtime/bs_stdlib_mini.cmi runtime/js.cmi runtime/js.cmj
 o runtime/caml_string_extern.cmi runtime/caml_string_extern.cmj : cc runtime/caml_string_extern.res | runtime/bs_stdlib_mini.cmi runtime/js.cmi runtime/js.cmj
 o runtime/caml_undefined_extern.cmi runtime/caml_undefined_extern.cmj : cc runtime/caml_undefined_extern.res | runtime/bs_stdlib_mini.cmi runtime/js.cmi runtime/js.cmj
diff --git a/jscomp/test/omit_trailing_undefined_in_external_calls.js b/jscomp/test/omit_trailing_undefined_in_external_calls.js
index 7a225b6f1d..12603d50f5 100644
--- a/jscomp/test/omit_trailing_undefined_in_external_calls.js
+++ b/jscomp/test/omit_trailing_undefined_in_external_calls.js
@@ -9,7 +9,11 @@ SomeModule.formatDate(new Date(), {
       someOption: true
     });
 
-var x = SomeModule.formatDate(new Date(), undefined, true);
+SomeModule.formatDate(new Date(), undefined, true);
+
+(42).toString();
+
+var x = new RegExp("ab+c");
 
 exports.x = x;
 /*  Not a pure module */
diff --git a/jscomp/test/omit_trailing_undefined_in_external_calls.res b/jscomp/test/omit_trailing_undefined_in_external_calls.res
index 4e4fca946d..07b4ac6e3e 100644
--- a/jscomp/test/omit_trailing_undefined_in_external_calls.res
+++ b/jscomp/test/omit_trailing_undefined_in_external_calls.res
@@ -9,3 +9,11 @@ external formatDate: (Js.Date.t, ~options: dateFormatOptions=?, ~done: bool=?) =
 let x = formatDate(Js.Date.make())
 let x = formatDate(Js.Date.make(), ~options={someOption: true})
 let x = formatDate(Js.Date.make(), ~done=true)
+
+@send external floatToString: (float, ~radix: int=?) => string = "toString"
+
+let x = floatToString(42.)
+
+@new external regExpFromString: (string, ~flags: string=?) => Js.Re.t = "RegExp"
+
+let x = regExpFromString("ab+c")
\ No newline at end of file