diff --git a/system/libraries/Encrypt.php b/system/libraries/Encrypt.php
index 656d51b..035ce8f 100644
--- a/system/libraries/Encrypt.php
+++ b/system/libraries/Encrypt.php
@@ -141,7 +141,7 @@
 	{
 		$key = $this->get_key($key);
 		
-		if ( ! preg_match('/[a-zA-Z0-9\/\+=]/', $string))
+		if (preg_match('/[^a-zA-Z0-9\/\+=]/', $string))
 		{
 			return FALSE;
 		}