diff --git a/doc/src/sgml/indexam.sgml b/doc/src/sgml/indexam.sgml
index f69f15627c..9957d1959d 100644
--- a/doc/src/sgml/indexam.sgml
+++ b/doc/src/sgml/indexam.sgml
@@ -546,7 +546,7 @@ amrescan (IndexScanDesc scan,
 
   <para>
 <programlisting>
-boolean
+bool
 amgettuple (IndexScanDesc scan,
             ScanDirection direction);
 </programlisting>