diff --git a/misc/wasm/wasm_exec.js b/misc/wasm/wasm_exec.js
index 231185a123..22b19fbe80 100644
--- a/misc/wasm/wasm_exec.js
+++ b/misc/wasm/wasm_exec.js
@@ -1,6 +1,7 @@
 // Copyright 2018 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
+"use strict";
 
 (() => {
 	// Map multiple JavaScript environments to a single common API,