diff --git a/system/libraries/Form_validation.php b/system/libraries/Form_validation.php
index 32cdc6bd..42fe0241 100644
--- a/system/libraries/Form_validation.php
+++ b/system/libraries/Form_validation.php
@@ -1062,7 +1062,7 @@ class CI_Form_validation {
 	{
 		return is_array($str)
 			? (empty($str) === FALSE)
-			: (trim($str) !== '');
+			: (trim($str ?? '') !== '');
 	}
 
 	// --------------------------------------------------------------------