diff --git a/src/Illuminate/Notifications/Messages/MailMessage.php b/src/Illuminate/Notifications/Messages/MailMessage.php
index 5a53283e9b46..9b3bab2ae803 100644
--- a/src/Illuminate/Notifications/Messages/MailMessage.php
+++ b/src/Illuminate/Notifications/Messages/MailMessage.php
@@ -36,7 +36,7 @@ class MailMessage extends SimpleMessage implements Renderable
      *
      * @var string|null
      */
-    public $theme = 'default';
+    public $theme;
 
     /**
      * The "from" information for the message.
diff --git a/tests/Integration/Notifications/SendingMailNotificationsTest.php b/tests/Integration/Notifications/SendingMailNotificationsTest.php
index 3cfd9142acee..2141a09ff4ff 100644
--- a/tests/Integration/Notifications/SendingMailNotificationsTest.php
+++ b/tests/Integration/Notifications/SendingMailNotificationsTest.php
@@ -74,7 +74,6 @@ public function test_mail_is_sent()
             'email' => 'taylor@laravel.com',
         ]);
 
-        $this->markdown->shouldReceive('theme')->once()->andReturnSelf();
         $this->markdown->shouldReceive('render')->once()->andReturn('htmlContent');
         $this->markdown->shouldReceive('renderText')->once()->andReturn('textContent');
 
@@ -119,7 +118,6 @@ public function test_mail_is_sent_to_named_address()
             'name' => 'Taylor Otwell',
         ]);
 
-        $this->markdown->shouldReceive('theme')->once()->andReturnSelf();
         $this->markdown->shouldReceive('render')->once()->andReturn('htmlContent');
         $this->markdown->shouldReceive('renderText')->once()->andReturn('textContent');
 
@@ -163,7 +161,6 @@ public function test_mail_is_sent_with_subject()
             'email' => 'taylor@laravel.com',
         ]);
 
-        $this->markdown->shouldReceive('theme')->once()->andReturnSelf();
         $this->markdown->shouldReceive('render')->once()->andReturn('htmlContent');
         $this->markdown->shouldReceive('renderText')->once()->andReturn('textContent');
 
@@ -197,7 +194,6 @@ public function test_mail_is_sent_to_multiple_adresses()
             'email' => 'taylor@laravel.com',
         ]);
 
-        $this->markdown->shouldReceive('theme')->once()->andReturnSelf();
         $this->markdown->shouldReceive('render')->once()->andReturn('htmlContent');
         $this->markdown->shouldReceive('renderText')->once()->andReturn('textContent');