diff --git a/wp-includes/class-wp.php b/wp-includes/class-wp.php
index 9e4b769b7c..deea1e6df8 100644
--- a/wp-includes/class-wp.php
+++ b/wp-includes/class-wp.php
@@ -186,6 +186,7 @@ class WP {
 			// Look for matches.
 			$request_match = $request;
 			if ( empty( $req_uri ) ) {
+				// An empty request could only match against ^$ regex
 				if ( isset( $rewrite['$'] ) ) {
 					$this->matched_rule = '$';
 					$query = $rewrite['$'];