diff --git a/src/wp-includes/pluggable.php b/src/wp-includes/pluggable.php
index 65750be262..ef2821fb2a 100644
--- a/src/wp-includes/pluggable.php
+++ b/src/wp-includes/pluggable.php
@@ -647,7 +647,7 @@ function wp_validate_auth_cookie($cookie = '', $scheme = '') {
 	$key = wp_hash($username . $pass_frag . '|' . $expiration, $scheme);
 	$hash = hash_hmac('md5', $username . '|' . $expiration, $key);
 
-	if ( $hmac != $hash ) {
+	if ( hash_hmac( 'md5', $hmac, $key ) !== hash_hmac( 'md5', $hash, $key ) ) {
 		/**
 		 * Fires if a bad authentication cookie hash is encountered.
 		 *