diff --git a/doc/src/sgml/libpq.sgml b/doc/src/sgml/libpq.sgml
index 08bd5121926..298c4b38ef9 100644
--- a/doc/src/sgml/libpq.sgml
+++ b/doc/src/sgml/libpq.sgml
@@ -1,6 +1,6 @@
 <!-- doc/src/sgml/libpq.sgml -->
 
-<chapter id="libpq">
+<chapter id="libpq" xreflabel="libpq">
  <title><application>libpq</application> &mdash; C Library</title>
 
  <indexterm zone="libpq">
diff --git a/doc/src/sgml/plpython.sgml b/doc/src/sgml/plpython.sgml
index bee817ea822..cb065bf5f88 100644
--- a/doc/src/sgml/plpython.sgml
+++ b/doc/src/sgml/plpython.sgml
@@ -1,6 +1,6 @@
 <!-- doc/src/sgml/plpython.sgml -->
 
-<chapter id="plpython">
+<chapter id="plpython" xreflabel="PL/Python">
  <title>PL/Python &mdash; Python Procedural Language</title>
 
  <indexterm zone="plpython"><primary>PL/Python</primary></indexterm>