diff --git a/EventListener/AlertifyListener.php b/EventListener/AlertifyListener.php
index 4133444..b24ecdd 100644
--- a/EventListener/AlertifyListener.php
+++ b/EventListener/AlertifyListener.php
@@ -57,22 +57,31 @@ public function onKernelResponse(FilterResponseEvent $event)
 
     /**
      * Injects the alertify view into the given Response just before </body> tag.
+     *
+     * @param Response $response
+     * @param Request  $request
+     *
+     * @throws IncompatibleStatusCodeException
      */
     protected function injectAlertify(Response $response, Request $request)
     {
-        if ($response instanceof RedirectResponse) {
-            return;
-        }
-
         $content = $response->getContent();
         $endBodyPos = strripos($content, '</body>');
         $hasBody = false !== $endBodyPos;
         $hasMetaRefresh = false !== strripos($content, 'http-equiv="refresh"');
+        $forceInject = $response->headers->get('X-Inject-Alertify', false);
         $isRedirectResponse = $response instanceof RedirectResponse;
 
-        if ($hasBody && !$hasMetaRefresh && !$isRedirectResponse) {
+        if ($hasBody && !$hasMetaRefresh && !$isRedirectResponse || $forceInject) {
+            if ($response->getStatusCode() === 204) {
+                throw new IncompatibleStatusCodeException();
+            }
             $alertify = $this->alertifySessionHandler->handle($this->session, $this->twig);
-            $content = substr($content, 0, $endBodyPos).$alertify.substr($content, $endBodyPos);
+            if ($endBodyPos) {
+                $content = substr($content, 0, $endBodyPos).$alertify.substr($content, $endBodyPos);
+            } else {
+                $content .= $alertify;
+            }
             $response->setContent($content);
         }
     }
diff --git a/Exception/IncompatibleStatusCodeException.php b/Exception/IncompatibleStatusCodeException.php
new file mode 100644
index 0000000..22cd3ec
--- /dev/null
+++ b/Exception/IncompatibleStatusCodeException.php
@@ -0,0 +1,21 @@
+<?php
+
+namespace Troopers\AlertifyBundle\Exception;
+
+/**
+ * Class IncompatibleStatusCodeException.
+ */
+class IncompatibleStatusCodeException extends \Exception
+{
+    /**
+     * IncompatibleStatusCodeException constructor.
+     *
+     * @param string $message
+     * @param int    $code
+     * @param null   $previous
+     */
+    public function __construct($message = "Status code 204 can't have content, please choose another one.", $code = 544, $previous = null)
+    {
+        parent::__construct($message, $code, $previous);
+    }
+}
diff --git a/README.md b/README.md
index ca2b5a5..c0aec99 100644
--- a/README.md
+++ b/README.md
@@ -31,5 +31,5 @@ With Alertify, give the final user a unique and harmnized view f your notificati
 - [Installation](https://github.com/Troopers/TroopersAlertifyBundle/blob/master/Resources/doc/installation.md)
 - [Configuration](https://github.com/Troopers/TroopersAlertifyBundle/blob/master/Resources/doc/configuration.md)
 - [Getting started](https://github.com/Troopers/TroopersAlertifyBundle/blob/master/Resources/doc/getting_started.md)
-- [Advanced (modal, confirmation modal)](https://github.com/Troopers/TroopersAlertifyBundle/blob/master/Resources/doc/advanced.md)
+- [Advanced (modal, confirmation modal, custom header)](https://github.com/Troopers/TroopersAlertifyBundle/blob/master/Resources/doc/advanced.md)
 - [Pro tips](https://github.com/Troopers/TroopersAlertifyBundle/blob/master/Resources/doc/pro_tips.md)
diff --git a/Resources/doc/advanced.md b/Resources/doc/advanced.md
index d7afa72..3f2e801 100644
--- a/Resources/doc/advanced.md
+++ b/Resources/doc/advanced.md
@@ -71,3 +71,15 @@ Instead of that, the js we'll be ran.
 ```html
     <a href="/your_url" class="btn btn-mini btn-danger" data-toggle="confirm" data-title="Are you sure ?" data-body="Kittens will suffer ! Do you confirm ?" data-cancel-button-class="cancel" data-confirm-button-class="danger">Burn some cats</a>
 ```
+
+## Custom header
+
+If you want to force the trigger of an alert, after an ajax call for example, you need to send through the response a custom header : `X-Inject-Alertify`.  When its value is set to `true`, then the alert append at the end of the response content, even if it is empty. Note that the `204` status code (No content) is incompatible with this header, as the 204 response MUST NOT include a message-body.
+
+## Example :
+
+```php
+return new Response(null, 200, [
+	'X-Inject-Alertify' => true
+]);
+```
\ No newline at end of file