diff --git a/code/libraries/koowa/filter/boolean.php b/code/libraries/koowa/filter/boolean.php
index <HASH>..<HASH> 100644
--- a/code/libraries/koowa/filter/boolean.php
+++ b/code/libraries/koowa/filter/boolean.php
@@ -41,6 +41,6 @@ class KFilterBoolean extends KFilterAbstract
 	 */
 	protected function _sanitize($value)
 	{
-		return $value !== '' ? (bool) filter_var($value, FILTER_VALIDATE_BOOLEAN) : NULL;
+		return (bool) filter_var($value, FILTER_VALIDATE_BOOLEAN);
 	}
 }
\ No newline at end of file
Always sanitize as boolean.