diff --git a/atom/browser/lib/init.coffee b/atom/browser/lib/init.coffee
index 069eed8d1b53..1299364d2fa6 100644
--- a/atom/browser/lib/init.coffee
+++ b/atom/browser/lib/init.coffee
@@ -92,5 +92,8 @@ app.setAppPath packagePath
 # Load the chrome extension support.
 require './chrome-extension'
 
+# Set main startup script of the app.
+mainStartupScript = packageJson.main or 'index.js'
+
 # Finally load app's main.js and transfer control to C++.
-Module._load path.join(packagePath, packageJson.main), Module, true
+Module._load path.join(packagePath, mainStartupScript), Module, true
diff --git a/docs/tutorial/quick-start.md b/docs/tutorial/quick-start.md
index 197cf0d3b32b..8fc696e0bcda 100644
--- a/docs/tutorial/quick-start.md
+++ b/docs/tutorial/quick-start.md
@@ -67,6 +67,9 @@ like this:
 }
 ```
 
+__Note__: If the `main` field is not present in `package.json`, Electron will
+attempt to load an `index.js`.
+
 The `main.js` should create windows and handle system events, a typical
 example being: