diff --git a/doc/src/sgml/ref/merge.sgml b/doc/src/sgml/ref/merge.sgml
index cbb5b38a3e..7f73f3d89c 100644
--- a/doc/src/sgml/ref/merge.sgml
+++ b/doc/src/sgml/ref/merge.sgml
@@ -4,6 +4,9 @@ PostgreSQL documentation
 -->
 
 <refentry id="sql-merge">
+ <indexterm zone="sql-merge">
+  <primary>MERGE</primary>
+ </indexterm>
 
  <refmeta>
   <refentrytitle>MERGE</refentrytitle>