diff --git a/script/build-main.ts b/script/build-main.ts
index 372b024..cbca964 100644
--- a/script/build-main.ts
+++ b/script/build-main.ts
@@ -19,7 +19,6 @@ const argv = minimist(process.argv.slice(2))
 const opts = options(argv.env)
 const TAG = '[build-main.ts]'
 const spinner = ora(`${TAG} Electron build...`)
-process.env.NODE_ENV = argv.env
 
 if (argv.watch) {
   waitOn({ port: process.env.PORT as string }).then(msg => {
@@ -32,7 +31,13 @@ if (argv.watch) {
     watcher.on('event', ev => {
       if (ev.code === 'END') {
         if (child) child.kill()
-        child = spawn(electron as any, [join(__dirname, `../${main}`)], { stdio: 'inherit' })
+        child = spawn(
+          electron as any,
+          [join(__dirname, `../${main}`)],
+          {
+            stdio: 'inherit',
+            env: Object.assign(process.env, { NODE_ENV: argv.env }),
+          })
       } else if (ev.code === 'ERROR') {
         console.log(ev.error)
       }
diff --git a/typings/global.d.ts b/typings/global.d.ts
index 42be2a3..22db89b 100644
--- a/typings/global.d.ts
+++ b/typings/global.d.ts
@@ -1,7 +1,7 @@
 
 declare namespace NodeJS {
   interface ProcessEnv {
-    NODE_ENV: 'development' | 'production'
+    readonly NODE_ENV: 'development' | 'production'
     readonly PORT: string
   }
 }