diff --git a/VERSION b/VERSION
index 8c9698a..aaf8be7 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-1.3.4
\ No newline at end of file
+1.3.5
\ No newline at end of file
diff --git a/flight/Engine.php b/flight/Engine.php
index ea6f6f9..0d95262 100644
--- a/flight/Engine.php
+++ b/flight/Engine.php
@@ -284,7 +284,7 @@ class Engine {
         $response = $this->response();
         $router = $this->router();
 
-        // Allow post-filters to run
+        // Allow filters to run
         $this->after('start', function() use ($self) {
             $self->stop();
         });
@@ -331,11 +331,29 @@ class Engine {
      *
      * @param int $code HTTP status code
      */
-    public function _stop($code = 200) {
-        $this->response()
-            ->status($code)
-            ->write(ob_get_clean())
-            ->send();
+    public function _stop($code = null) {
+        $response = $this->response();
+
+        if (!$response->sent()) {
+            if ($code !== null) {
+                $response->status($code);
+            }
+
+            $response->write(ob_get_clean());
+
+            $response->send();
+        }
+    }
+
+    /**
+     * Routes a URL to a callback function.
+     *
+     * @param string $pattern URL pattern to match
+     * @param callback $callback Callback function
+     * @param boolean $pass_route Pass the matching route object to the callback
+     */
+    public function _route($pattern, $callback, $pass_route = false) {
+        $this->router()->map($pattern, $callback, $pass_route);
     }
 
     /**
@@ -366,7 +384,8 @@ class Engine {
         );
 
         try {
-            $this->response(false)
+            $this->response()
+                ->clear()
                 ->status(500)
                 ->write($msg)
                 ->send();
@@ -383,7 +402,8 @@ class Engine {
      * Sends an HTTP 404 response when a URL is not found.
      */
     public function _notFound() {
-        $this->response(false)
+        $this->response()
+            ->clear()
             ->status(404)
             ->write(
                 '<h1>404 Not Found</h1>'.
@@ -393,17 +413,6 @@ class Engine {
             ->send();
     }
 
-    /**
-     * Routes a URL to a callback function.
-     *
-     * @param string $pattern URL pattern to match
-     * @param callback $callback Callback function
-     * @param boolean $pass_route Pass the matching route object to the callback
-     */
-    public function _route($pattern, $callback, $pass_route = false) {
-        $this->router()->map($pattern, $callback, $pass_route);
-    }
-
     /**
      * Redirects the current request to another URL.
      *
@@ -422,7 +431,8 @@ class Engine {
             $url = $base . preg_replace('#/+#', '/', '/' . $url);
         }
 
-        $this->response(false)
+        $this->response()
+            ->clear()
             ->status($code)
             ->header('Location', $url)
             ->write($url)
diff --git a/flight/net/Response.php b/flight/net/Response.php
index cab0305..c4f6ec7 100644
--- a/flight/net/Response.php
+++ b/flight/net/Response.php
@@ -29,6 +29,11 @@ class Response {
      */
     protected $body;
 
+    /**
+     * @var bool HTTP response sent
+     */
+    protected $sent = false;
+
     /**
      * @var array HTTP status codes
      */
@@ -247,9 +252,7 @@ class Response {
         }
 
         // Send content length
-        $length = (extension_loaded('mbstring')) ?
-            mb_strlen($this->body, 'latin1') :
-            strlen($this->body);
+        $length = $this->getContentLength();
 
         if ($length > 0) {
             header('Content-Length: '.$length);
@@ -258,6 +261,24 @@ class Response {
         return $this;
     }
 
+    /**
+     * Gets the content length.
+     *
+     * @return string Content length
+     */
+    public function getContentLength() {
+        return extension_loaded('mbstring') ?
+            mb_strlen($this->body, 'latin1') :
+            strlen($this->body);
+    }
+
+    /**
+     * Gets whether response was sent.
+     */
+    public function sent() {
+        return $this->sent;
+    }
+
     /**
      * Sends a HTTP response.
      */
@@ -271,6 +292,8 @@ class Response {
         }
 
         echo $this->body;
+
+        $this->sent = true;
     }
 }