diff --git a/doc/src/sgml/ref/commit_prepared.sgml b/doc/src/sgml/ref/commit_prepared.sgml
index 2af677fcb0625bd88cf8d99adb280a7e16318766..ecd0c525f2077789c7d7ba774677cb4c2af7779c 100644
--- a/doc/src/sgml/ref/commit_prepared.sgml
+++ b/doc/src/sgml/ref/commit_prepared.sgml
@@ -83,6 +83,18 @@ COMMIT PREPARED 'foobar';
 
  </refsect1>
 
+ <refsect1>
+  <title>Compatibility</title>
+
+  <para>
+   <command>COMMIT PREPARED</command> is a
+   <productname>PostgreSQL</productname> extension.  It is intended for use by
+   external transaction management systems, some of which are covered by
+   standards (such as X/Open XA), but the SQL side of those systems is not
+   standardized.
+  </para>
+ </refsect1>
+
  <refsect1>
   <title>See Also</title>
 
diff --git a/doc/src/sgml/ref/prepare_transaction.sgml b/doc/src/sgml/ref/prepare_transaction.sgml
index a10aa35d386cd98d7fa2f64b57d2fa594baddc50..a379819a0aac8b6cb115e92df78475b5feded4e2 100644
--- a/doc/src/sgml/ref/prepare_transaction.sgml
+++ b/doc/src/sgml/ref/prepare_transaction.sgml
@@ -156,6 +156,18 @@ PREPARE TRANSACTION 'foobar';
 </programlisting></para>
  </refsect1>
 
+ <refsect1>
+  <title>Compatibility</title>
+
+  <para>
+   <command>PREPARE TRANSACTION</command> is a
+   <productname>PostgreSQL</productname> extension.  It is intended for use by
+   external transaction management systems, some of which are covered by
+   standards (such as X/Open XA), but the SQL side of those systems is not
+   standardized.
+  </para>
+ </refsect1>
+
  <refsect1>
   <title>See Also</title>
 
diff --git a/doc/src/sgml/ref/rollback_prepared.sgml b/doc/src/sgml/ref/rollback_prepared.sgml
index 9592b92f32181095c2e7b26a34244d74cb47e01d..514e5ae441a345b77e8261ab1e088247f998852d 100644
--- a/doc/src/sgml/ref/rollback_prepared.sgml
+++ b/doc/src/sgml/ref/rollback_prepared.sgml
@@ -83,6 +83,18 @@ ROLLBACK PREPARED 'foobar';
 
  </refsect1>
 
+ <refsect1>
+  <title>Compatibility</title>
+
+  <para>
+   <command>ROLLBACK PREPARED</command> is a
+   <productname>PostgreSQL</productname> extension.  It is intended for use by
+   external transaction management systems, some of which are covered by
+   standards (such as X/Open XA), but the SQL side of those systems is not
+   standardized.
+  </para>
+ </refsect1>
+
  <refsect1>
   <title>See Also</title>