diff --git a/lib/Router/Endpoints/ViewInBrowser.php b/lib/Router/Endpoints/ViewInBrowser.php
index 418e035e20..ab61e6c446 100644
--- a/lib/Router/Endpoints/ViewInBrowser.php
+++ b/lib/Router/Endpoints/ViewInBrowser.php
@@ -39,11 +39,6 @@ class ViewInBrowser {
       Newsletter::getByHash($data->newsletter_hash);
     if(!$data->newsletter) return false;
 
-    // queue is optional; if defined, get it
-    $data->queue = (!empty($data->queue_id)) ?
-      SendingQueue::findOne($data->queue_id) :
-      SendingQueue::where('newsletter_id', $data->newsletter->id)->findOne();
-
     // subscriber is optional; if exists, token must validate
     $data->subscriber = (!empty($data->subscriber_id)) ?
       Subscriber::findOne($data->subscriber_id) :
@@ -53,6 +48,15 @@ class ViewInBrowser {
          !Subscriber::verifyToken($data->subscriber->email, $data->subscriber_token)
       ) return false;
     }
+
+    // if newsletter ID is defined then subscriber must exist
+    if($data->newsletter_id && !$data->subscriber) return false;
+
+    // queue is optional; if defined, get it
+    $data->queue = (!empty($data->queue_id)) ?
+      SendingQueue::findOne($data->queue_id) :
+      SendingQueue::where('newsletter_id', $data->newsletter->id)->findOne();
+
     // if queue and subscriber exist and newsletter is not being previewed,
     // subscriber must have received the newsletter
     if(empty($data->preview) &&
diff --git a/tests/unit/Router/Endpoints/ViewInBrowserTest.php b/tests/unit/Router/Endpoints/ViewInBrowserTest.php
index 58edf88ad9..a152f3b0ff 100644
--- a/tests/unit/Router/Endpoints/ViewInBrowserTest.php
+++ b/tests/unit/Router/Endpoints/ViewInBrowserTest.php
@@ -37,7 +37,7 @@ class ViewInBrowserRouterTest extends MailPoetTest {
 
   function testItAbortsWhenBrowserPreviewDataIsMissing() {
     $view_in_browser = Stub::make($this->view_in_browser, array(
-      '_abort' => Stub::exactly(2, function () { })
+      '_abort' => Stub::exactly(2, function() { })
     ), $this);
     // newsletter ID is required
     $data = $this->browser_preview_data;
@@ -51,7 +51,7 @@ class ViewInBrowserRouterTest extends MailPoetTest {
 
   function testItAbortsWhenBrowserPreviewDataIsInvalid() {
     $view_in_browser = Stub::make($this->view_in_browser, array(
-      '_abort' => Stub::exactly(3, function () { })
+      '_abort' => Stub::exactly(3, function() { })
     ), $this);
     // newsletter ID is invalid
     $data = $this->browser_preview_data;
@@ -72,7 +72,7 @@ class ViewInBrowserRouterTest extends MailPoetTest {
     $subscriber = $this->subscriber;
     $subscriber->email = 'random@email.com';
     $subscriber->save();
-    $data = (object) array_merge(
+    $data = (object)array_merge(
       $this->browser_preview_data,
       array(
         'queue' => $this->queue,
@@ -83,8 +83,14 @@ class ViewInBrowserRouterTest extends MailPoetTest {
     expect($this->view_in_browser->_validateBrowserPreviewData($data))->false();
   }
 
+  function testItFailsValidationWhenNewsletterIdIsProvidedButSubscriberDoesNotExist() {
+    $data = (object)$this->browser_preview_data;
+    $data->subscriber_id = false;
+    expect($this->view_in_browser->_validateBrowserPreviewData($data))->false();
+  }
+
   function testItFailsValidationWhenSubscriberIsNotOnProcessedList() {
-    $data = (object) $this->browser_preview_data;
+    $data = (object)$this->browser_preview_data;
     $result = $this->view_in_browser->_validateBrowserPreviewData($data);
     expect($result)->notEmpty();
     $queue = $this->queue;
@@ -95,7 +101,7 @@ class ViewInBrowserRouterTest extends MailPoetTest {
   }
 
   function testItDoesNotRequireWpUsersToBeOnProcessedListWhenPreviewIsEnabled() {
-    $data = (object) array_merge(
+    $data = (object)array_merge(
       $this->browser_preview_data,
       array(
         'queue' => $this->queue,
@@ -117,7 +123,7 @@ class ViewInBrowserRouterTest extends MailPoetTest {
 
   function testItReturnsViewActionResult() {
     $view_in_browser = Stub::make($this->view_in_browser, array(
-      '_displayNewsletter' => Stub::exactly(1, function () { })
+      '_displayNewsletter' => Stub::exactly(1, function() { })
     ), $this);
     $view_in_browser->data = $view_in_browser->_processBrowserPreviewData($this->browser_preview_data);
     $view_in_browser->view();