diff --git a/src/Adoy/FastCGI/Client.php b/src/Adoy/FastCGI/Client.php
index 0a7d8a5..a5a946e 100644
--- a/src/Adoy/FastCGI/Client.php
+++ b/src/Adoy/FastCGI/Client.php
@@ -10,6 +10,7 @@
 namespace Adoy\FastCGI;
 
 class TimedOutException extends \Exception {}
+class ForbiddenException extends \Exception {}
 
 /**
  * Handles communication with a FastCGI application
@@ -547,6 +548,12 @@ public function wait_for_response($requestId, $timeoutMs = 0) {
                 throw new TimedOutException('Read timed out');
             }
 
+            if ($info['unread_bytes'] == 0
+                    && $info['blocked']
+                    && $info['eof']) {
+                throw new ForbiddenException('Not in white list. Check listen.allowed_clients.');
+            }
+
             throw new \Exception('Read failed');
         }