diff --git a/system/libraries/Encrypt.php b/system/libraries/Encrypt.php
index 6796092..73ab8ca 100644
--- a/system/libraries/Encrypt.php
+++ b/system/libraries/Encrypt.php
@@ -165,7 +165,7 @@
 	 */
 	public function decode($string, $key = '')
 	{
-		if (preg_match('/[^a-zA-Z0-9\/\+=]/', $string))
+		if (preg_match('/[^a-zA-Z0-9\/\+=]/', $string) OR base64_encode(base64_decode($string)) !== $string)
 		{
 			return FALSE;
 		}