diff --git a/doc/src/sgml/ref/pgbench.sgml b/doc/src/sgml/ref/pgbench.sgml
index ca16088118..15ee7c0f2b 100644
--- a/doc/src/sgml/ref/pgbench.sgml
+++ b/doc/src/sgml/ref/pgbench.sgml
@@ -473,6 +473,13 @@ pgbench options d
prepared: use extended query protocol with prepared statements.
+
+ Because in "prepared" mode pgbench reuses
+ the parse analysis result for the second and subsequent query
+ iteration, pgbench runs faster in the
+ prepared mode than in other modes.
+
+
The default is simple query protocol. (See
for more information.)