diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 6cc162bb7a..67b8adaafb 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -141,6 +141,12 @@
square root
sqrt(2.0)
+
+ cbrt(float8)
+ float8
+ cube root
+ cbrt(27.0)
+
trunc(float8)
float8