diff --git a/system/libraries/Encryption.php b/system/libraries/Encryption.php
index 0b759eb..e002c28 100644
--- a/system/libraries/Encryption.php
+++ b/system/libraries/Encryption.php
@@ -901,7 +901,7 @@
 	{
 		if (self::$func_override)
 		{
-			return mb_substr($str, $start, $length);
+			return mb_substr($str, $start, $length, '8bit');
 		}
 
 		return isset($length)