diff --git a/doc/src/sgml/indexam.sgml b/doc/src/sgml/indexam.sgml
index a26ed32867..fcdb8c3ec4 100644
--- a/doc/src/sgml/indexam.sgml
+++ b/doc/src/sgml/indexam.sgml
@@ -567,7 +567,7 @@ amrescan (IndexScanDesc scan,
 
   <para>
 <programlisting>
-boolean
+bool
 amgettuple (IndexScanDesc scan,
             ScanDirection direction);
 </programlisting>