diff --git a/doc/src/sgml/indexam.sgml b/doc/src/sgml/indexam.sgml
index 320f50f03c0..a7828cbed03 100644
--- a/doc/src/sgml/indexam.sgml
+++ b/doc/src/sgml/indexam.sgml
@@ -528,7 +528,7 @@ amrescan (IndexScanDesc scan,
 
   <para>
 <programlisting>
-boolean
+bool
 amgettuple (IndexScanDesc scan,
             ScanDirection direction);
 </programlisting>