diff --git a/docs/source/user-guide/sql/scalar_functions.md b/docs/source/user-guide/sql/scalar_functions.md
index d4eb5944ad09..41b5a354abc1 100644
--- a/docs/source/user-guide/sql/scalar_functions.md
+++ b/docs/source/user-guide/sql/scalar_functions.md
@@ -1956,6 +1956,7 @@ from_unixtime(expression)
 - [array_to_string](#array_to_string)
 - [cardinality](#cardinality)
 - [empty](#empty)
+- [flatten](#flatten)
 - [generate_series](#generate_series)
 - [list_append](#list_append)
 - [list_sort](#list_sort)