diff --git a/contrib/pg_plan_advice/README b/contrib/pg_plan_advice/README
index 2ea61e9bc41..2be40f0eba6 100644
--- a/contrib/pg_plan_advice/README
+++ b/contrib/pg_plan_advice/README
@@ -263,5 +263,3 @@ good idea to incorporate that ability at some future point, as pg_hint_plan
 does. However, since the primary goal of the initial development work is to be
 able to induce the planner to recreate a desired plan that worked well in
 the past, this has not been included in the initial development effort.
-
-XXX Need to investigate whether and how well supplying advice works with GEQO
diff --git a/doc/src/sgml/pgplanadvice.sgml b/doc/src/sgml/pgplanadvice.sgml
index b1395ec951e..0116b0d88f7 100644
--- a/doc/src/sgml/pgplanadvice.sgml
+++ b/doc/src/sgml/pgplanadvice.sgml
@@ -812,6 +812,22 @@ EXPLAIN (COSTS OFF)
    force the choice of a plan which the planner refused to consider in the
    first place.
   </para>
+
+  <para>
+   One consequence of the limitation described in the previous paragraph is
+   that plan advice works only probabilistically when
+   <link linkend="geqo"><acronym>GEQO</acronym></link> is used. Even if plans
+   compatible with the supplied advice exist, there is no guarantee that any
+   of them will be a part of the randomly generated pool of candidates. If
+   not, the planner will generate a plan that does not comply with the
+   supplied advice, with some parts of that plan marked disabled. If you
+   supply advice that only mildly constrains join planning,
+   <acronym>GEQO</acronym> will usually manage to find a plan that conforms
+   with it; but if you wish to constrain it more substantially, you may need
+   to disable <acronym>GEQO</acronym> in order to obtain satisfactory results.
+   Note that scan advice is not affected by this limitation because it does
+   not constrain the join order.
+  </para>
  </sect2>
 
  <sect2 id="pgplanadvice-author">