diff --git a/platform/web/detect.py b/platform/web/detect.py
index f0e755049ad..a634a7ca8a4 100644
--- a/platform/web/detect.py
+++ b/platform/web/detect.py
@@ -158,7 +158,7 @@ def configure(env: "Environment"):
     env.AddMethod(create_template_zip, "CreateTemplateZip")
 
     # Closure compiler extern and support for ecmascript specs (const, let, etc).
-    env["ENV"]["EMCC_CLOSURE_ARGS"] = "--language_in ECMASCRIPT_2020"
+    env["ENV"]["EMCC_CLOSURE_ARGS"] = "--language_in ECMASCRIPT_2021"
 
     env["CC"] = "emcc"
     env["CXX"] = "em++"