diff --git a/doc/rbd/rbd-persistent-cache.rst b/doc/rbd/rbd-persistent-cache.rst
index 0bd39594283..6c5bb92f601 100644
--- a/doc/rbd/rbd-persistent-cache.rst
+++ b/doc/rbd/rbd-persistent-cache.rst
@@ -73,6 +73,10 @@ not enough capacity it will delete some cold cache files.
 
 Here are some important cache options correspond to the following settings:
 
+- ``immutable_object_cache_sock`` The path to the domain socket used for
+  communication between librbd clients and the ceph-immutable-object-cache
+  daemon.
+
 - ``immutable_object_cache_path`` The immutable object cache data directory.
 
 - ``immutable_object_cache_max_size`` The max size for immutable cache.