diff --git a/doc/src/sgml/runtime.sgml b/doc/src/sgml/runtime.sgml
index ac4934608c3..2f660e288e0 100644
--- a/doc/src/sgml/runtime.sgml
+++ b/doc/src/sgml/runtime.sgml
@@ -812,7 +812,8 @@ psql: could not connect to server: No such file or directory
When using System V semaphores,
PostgreSQL uses one semaphore per allowed connection
(), allowed autovacuum worker process
- () and allowed background
+ (), allowed WAL sender process
+ (), and allowed background
process (), in sets of 16.
Each such set will
also contain a 17th semaphore which contains a magic