diff --git a/doc/src/sgml/pgbuffercache.sgml b/doc/src/sgml/pgbuffercache.sgml
index 1d7d95f9d7d..685351f11eb 100644
--- a/doc/src/sgml/pgbuffercache.sgml
+++ b/doc/src/sgml/pgbuffercache.sgml
@@ -84,7 +84,8 @@
relforknumber
smallint
- Fork number within the relation
+ Fork number within the relation; see
+ include/storage/relfilenode.h>
@@ -98,7 +99,7 @@
usagecount
smallint
- Page LRU count
+ Clock-sweep access count