diff --git a/system/core/Common.php b/system/core/Common.php
index 09b73ef..2a80487 100644
--- a/system/core/Common.php
+++ b/system/core/Common.php
@@ -490,7 +490,7 @@
 		}
 		else
 		{
-			header($server_protocol.' '.$code.' '.$text, TRUE, $code);
+			header($server_protocol ?: 'HTTP/1.1'.' '.$code.' '.$text, TRUE, $code);
 		}
 	}
 }