diff --git a/platform/javascript/detect.py b/platform/javascript/detect.py
index c7235118039..68f47b40390 100644
--- a/platform/javascript/detect.py
+++ b/platform/javascript/detect.py
@@ -151,7 +151,7 @@ def configure(env):
     env.AddMethod(create_template_zip, "CreateTemplateZip")
 
     # Closure compiler extern and support for ecmascript specs (const, let, etc).
-    env["ENV"]["EMCC_CLOSURE_ARGS"] = "--language_in ECMASCRIPT6"
+    env["ENV"]["EMCC_CLOSURE_ARGS"] = "--language_in ECMASCRIPT_2021"
 
     env["CC"] = "emcc"
     env["CXX"] = "em++"