diff --git a/wp-includes/classes.php b/wp-includes/classes.php
index 4bcd9fe8f6..d91dd3e4d3 100644
--- a/wp-includes/classes.php
+++ b/wp-includes/classes.php
@@ -207,8 +207,8 @@ class WP {
 					$request_match = $req_uri . '/' . $request;
 				}
 
-				if (preg_match("!^$match!", $request_match, $matches) ||
-					preg_match("!^$match!", urldecode($request_match), $matches)) {
+				if (preg_match("#^$match#", $request_match, $matches) ||
+					preg_match("#^$match#", urldecode($request_match), $matches)) {
 					// Got a match.
 					$this->matched_rule = $match;