diff --git a/system/core/Input.php b/system/core/Input.php
index 30d528b8..3681f499 100644
--- a/system/core/Input.php
+++ b/system/core/Input.php
@@ -508,7 +508,7 @@ class CI_Input {
 				$which = FILTER_FLAG_IPV6;
 				break;
 			default:
-				$which = NULL;
+				$which = [];
 				break;
 		}