diff --git a/system/core/Security.php b/system/core/Security.php
index 6ed0f8d..8adc356 100755
--- a/system/core/Security.php
+++ b/system/core/Security.php
@@ -977,8 +977,8 @@
 			// We don't necessarily want to regenerate it with
 			// each page load since a page could contain embedded
 			// sub-pages causing this feature to fail
-			if (isset($_COOKIE[$this->_csrf_cookie_name]) &&
-				preg_match('#^[0-9a-f]{32}$#iS', $_COOKIE[$this->_csrf_cookie_name]) === 1)
+			if (isset($_COOKIE[$this->_csrf_cookie_name]) && is_string($_COOKIE[$this->_csrf_cookie_name])
+				&& preg_match('#^[0-9a-f]{32}$#iS', $_COOKIE[$this->_csrf_cookie_name]) === 1)
 			{
 				return $this->_csrf_hash = $_COOKIE[$this->_csrf_cookie_name];
 			}