diff --git a/doc/src/sgml/indexam.sgml b/doc/src/sgml/indexam.sgml
index 05102724ead..189179a5667 100644
--- a/doc/src/sgml/indexam.sgml
+++ b/doc/src/sgml/indexam.sgml
@@ -127,6 +127,7 @@ typedef struct IndexAmRoutine
     amcostestimate_function amcostestimate;
     amoptions_function amoptions;
     amproperty_function amproperty;     /* can be NULL */
+    amphasename_function amphasename;   /* can be NULL */