diff --git a/doc/src/sgml/pgbuffercache.sgml b/doc/src/sgml/pgbuffercache.sgml
index 59dbbd2b25e..3d9032efafb 100644
--- a/doc/src/sgml/pgbuffercache.sgml
+++ b/doc/src/sgml/pgbuffercache.sgml
@@ -45,9 +45,10 @@
  </para>
 
  <para>
-  The <function>pg_buffercache_numa_pages()</function> provides the same information
-  as <function>pg_buffercache_pages()</function> but is slower because it also
-  provides the <acronym>NUMA</acronym> node ID per shared buffer entry.
+  The <function>pg_buffercache_numa_pages()</function> provides
+  <acronym>NUMA</acronym> node mappings for shared buffer entries. This
+  information is not part of <function>pg_buffercache_pages()</function>
+  itself, as it is much slower to retrieve.
   The <structname>pg_buffercache_numa</structname> view wraps the function for
   convenient use.
  </para>