diff --git a/Response.php b/Response.php
index c1a2e1488..05f740b6a 100644
--- a/Response.php
+++ b/Response.php
@@ -628,7 +628,7 @@ public function isImmutable(): bool
     }
 
     /**
-     * Returns true if the response must be revalidated by caches.
+     * Returns true if the response must be revalidated by shared caches once it has become stale.
      *
      * This method indicates that the response must not be served stale by a
      * cache in any circumstance without first revalidating with the origin.