diff --git a/Message/Http/Header.php b/Message/Http/Header.php
index c1245f024..faa6bf109 100644
--- a/Message/Http/Header.php
+++ b/Message/Http/Header.php
@@ -220,7 +220,7 @@ class Header extends HeaderAbstract
                 $this->generate503();
                 break;
             default:
-                throw new \Exception('Unexpected header code');
+                $this->generate500();
         }
     }
 
@@ -282,6 +282,22 @@ class Header extends HeaderAbstract
 
     }
 
+    /**
+     * Generate predefined header.
+     *
+     * @return void
+     *
+     * @since  1.0.0
+     * @author Dennis Eichhorn <d.eichhorn@oms.com>
+     */
+    private function generate500()
+    {
+        $this->set('HTTP', 'HTTP/1.0 500 Internal Server Error');
+        $this->set('Status', 'Status: 500 Internal Server Error');
+        $this->set('Retry-After', 'Retry-After: 300');
+        http_response_code(500);
+    }
+
     /**
      * Generate predefined header.
      *