diff --git a/ext/js/js-core.c b/ext/js/js-core.c
index d5e36346a6..4f01f564ea 100644
--- a/ext/js/js-core.c
+++ b/ext/js/js-core.c
@@ -87,6 +87,12 @@ static VALUE _rb_js_eval_js(VALUE _, VALUE code_str) {
   return jsvalue_s_new(rb_js_abi_host_eval_js(&abi_str));
 }
 
+static VALUE _rb_js_eval_js_cstr(const char *code_str) {
+  rb_js_abi_host_string_t abi_str;
+  rb_js_abi_host_string_set(&abi_str, code_str);
+  return jsvalue_s_new(rb_js_abi_host_eval_js(&abi_str));
+}
+
 static VALUE _rb_js_is_js(VALUE _, VALUE obj) {
   if (!IS_JSVALUE(obj)) {
     return Qfalse;
@@ -370,6 +376,8 @@ void Init_js() {
   rb_define_module_function(rb_mJS, "try_convert", _rb_js_try_convert, 1);
   rb_define_module_function(rb_mJS, "eval", _rb_js_eval_js, 1);
   rb_define_module_function(rb_mJS, "global", _rb_js_global_this, 0);
+  rb_define_const(rb_mJS, "NULL", _rb_js_eval_js_cstr("return null"));
+  rb_define_const(rb_mJS, "UNDEFINED", _rb_js_eval_js_cstr("return undefined"));
 
   i_to_js = rb_intern("to_js");
   rb_cJS_Object = rb_define_class_under(rb_mJS, "Object", rb_cObject);
diff --git a/packages/npm-packages/ruby-wasm-wasi/test/js_from_rb.test.ts b/packages/npm-packages/ruby-wasm-wasi/test/js_from_rb.test.ts
index b76695a59b..33462f8a90 100644
--- a/packages/npm-packages/ruby-wasm-wasi/test/js_from_rb.test.ts
+++ b/packages/npm-packages/ruby-wasm-wasi/test/js_from_rb.test.ts
@@ -210,7 +210,7 @@ describe("Manipulation of JS from Ruby", () => {
 
   test("Guard null", async () => {
     const vm = await initRubyVM();
-    const result = vm.eval(`
+    const results = vm.eval(`
       require "js"
       intrinsics = JS.eval(<<-JS)
         return {
@@ -218,10 +218,13 @@ describe("Manipulation of JS from Ruby", () => {
           returnUndef(v) { return undefined },
         }
       JS
-      js_null = JS.eval("return null")
       o1 = intrinsics.call(:returnNull)
-      o1 == js_null
+      o2 = intrinsics.call(:returnUndef)
+      [o1 == JS::NULL, o2 == JS::UNDEFINED]
     `);
-    expect(result.toString()).toEqual("true");
+    const e1 = results.call("at", vm.eval("0"));
+    const e2 = results.call("at", vm.eval("1"));
+    expect(e1.toString()).toEqual("true");
+    expect(e2.toString()).toEqual("true");
   });
 });