diff --git a/doc/src/sgml/ref/select.sgml b/doc/src/sgml/ref/select.sgml
index 01d24a57c8b..2295f63c130 100644
--- a/doc/src/sgml/ref/select.sgml
+++ b/doc/src/sgml/ref/select.sgml
@@ -779,8 +779,8 @@ WINDOW window_name AS ( frame_clause> can be one of
-[ RANGE | ROWS ] frame_start>
-[ RANGE | ROWS ] BETWEEN frame_start> AND frame_end>
+{ RANGE | ROWS } frame_start>
+{ RANGE | ROWS } BETWEEN frame_start> AND frame_end>
where frame_start> and frame_end> can be
diff --git a/doc/src/sgml/syntax.sgml b/doc/src/sgml/syntax.sgml
index ff2c3e2b9a3..140b3bd12ef 100644
--- a/doc/src/sgml/syntax.sgml
+++ b/doc/src/sgml/syntax.sgml
@@ -1802,8 +1802,8 @@ FROM generate_series(1,10) AS s(i);
and the optional frame_clause
can be one of
-[ RANGE | ROWS ] frame_start>
-[ RANGE | ROWS ] BETWEEN frame_start> AND frame_end>
+{ RANGE | ROWS } frame_start>
+{ RANGE | ROWS } BETWEEN frame_start> AND frame_end>
where frame_start> and frame_end> can be
one of