diff --git a/src/wp-includes/pluggable.php b/src/wp-includes/pluggable.php
index cc16e8c8bde37..3dd629fa1990c 100644
--- a/src/wp-includes/pluggable.php
+++ b/src/wp-includes/pluggable.php
@@ -710,9 +710,10 @@ function wp_validate_auth_cookie( $cookie = '', $scheme = '' ) {
 		$username   = $cookie_elements['username'];
 		$hmac       = $cookie_elements['hmac'];
 		$token      = $cookie_elements['token'];
-		$expired    = $cookie_elements['expiration'];
 		$expiration = $cookie_elements['expiration'];
 
+		$expired = (int) $expiration;
+
 		// Allow a grace period for POST and Ajax requests.
 		if ( wp_doing_ajax() || 'POST' === $_SERVER['REQUEST_METHOD'] ) {
 			$expired += HOUR_IN_SECONDS;