diff --git a/payment/uc_paypal/uc_paypal.pages.inc b/payment/uc_paypal/uc_paypal.pages.inc
index a548d7b..6d83e31 100644
--- a/payment/uc_paypal/uc_paypal.pages.inc
+++ b/payment/uc_paypal/uc_paypal.pages.inc
@@ -78,11 +78,17 @@ function uc_paypal_ipn() {
   $response = drupal_http_request($host, array(
     'method' => 'POST',
     'data' => $req,
+    'Host' => $host,
   ));
 
   // TODO: Change this to property_exists when we have a PHP requirement >= 5.1.
   if (array_key_exists('error', $response)) {
-    watchdog('uc_paypal', 'IPN failed with HTTP error @error, code @code.', array('@error' => $response->error, '@code' => $response->code), WATCHDOG_ERROR);
+    if($response->code == '400') {
+      watchdog('uc_paypal', 'IPN failed with HTTP error @error, code @code. Please install @link, enable the module and check on the option "Override Drupal HTTP Request" in the chr configuration', array('@error' => $response->error, '@code' => $response->code, '@link' => l('Chr', array('external' => TRUE))), WATCHDOG_ERROR);
+    }
+    else {
+      watchdog('uc_paypal', 'IPN failed with HTTP error @error, code @code.', array('@error' => $response->error, '@code' => $response->code), WATCHDOG_ERROR);
+    }
     return;
   }