diff --git a/.eslintrc b/.eslintrc
index f4f88ad0..762f2ad1 100644
--- a/.eslintrc
+++ b/.eslintrc
@@ -1,6 +1,7 @@
 {
   "extends": ["standard", "standard-jsx"],
   "rules": {
-    "no-useless-escape": 0
+    "no-useless-escape": 0,
+    "prefer-const": "error"
   }
 }
diff --git a/lib/main-window.js b/lib/main-window.js
index c62108f4..dfe64281 100644
--- a/lib/main-window.js
+++ b/lib/main-window.js
@@ -6,9 +6,9 @@ const Config = require('electron-config')
 const config = new Config()
 
 var showMenu = process.platform !== 'win32'
-let windowSize = config.get('windowsize') || { width: 1080, height: 720 }
+const windowSize = config.get('windowsize') || { width: 1080, height: 720 }
 
-let mainWindow = new BrowserWindow({
+const mainWindow = new BrowserWindow({
   width: windowSize.width,
   height: windowSize.height,
   minWidth: 500,