diff --git a/src/Facebook/Authentication/AccessTokenMetadata.php b/src/Facebook/Authentication/AccessTokenMetadata.php
index 165433cb6..c86a0d912 100644
--- a/src/Facebook/Authentication/AccessTokenMetadata.php
+++ b/src/Facebook/Authentication/AccessTokenMetadata.php
@@ -210,7 +210,10 @@ public function getErrorSubcode()
     /**
      * DateTime when this access token expires.
      *
-     * @return \DateTime|null
+     * Note that a zero int value indicates the
+     * access token never expires.
+     *
+     * @return \DateTime|int|null
      */
     public function getExpiresAt()
     {