diff --git a/src/Illuminate/Encryption/EncryptionServiceProvider.php b/src/Illuminate/Encryption/EncryptionServiceProvider.php
index d27ed2826123..ad365becc4eb 100755
--- a/src/Illuminate/Encryption/EncryptionServiceProvider.php
+++ b/src/Illuminate/Encryption/EncryptionServiceProvider.php
@@ -2,6 +2,7 @@
 
 namespace Illuminate\Encryption;
 
+use RuntimeException;
 use Illuminate\Support\Str;
 use Illuminate\Support\ServiceProvider;
 
@@ -17,10 +18,18 @@ public function register()
         $this->app->singleton('encrypter', function ($app) {
             $config = $app->make('config')->get('app');
 
+            $key = $config['key'];
+
+            if (is_null($key) || $key === '') {
+                throw new RuntimeException(
+                    'The application encryption key is missing. Run php artisan key:generate to generate it.'
+                );
+            }
+
             // If the key starts with "base64:", we will need to decode the key before handing
             // it off to the encrypter. Keys may be base-64 encoded for presentation and we
             // want to make sure to convert them back to the raw bytes before encrypting.
-            if (Str::startsWith($key = $config['key'], 'base64:')) {
+            if (Str::startsWith($key, 'base64:')) {
                 $key = base64_decode(substr($key, 7));
             }