diff --git a/core/modules/views/src/Plugin/views/query/Sql.php b/core/modules/views/src/Plugin/views/query/Sql.php
index c481a85..9d1c4ca 100644
--- a/core/modules/views/src/Plugin/views/query/Sql.php
+++ b/core/modules/views/src/Plugin/views/query/Sql.php
@@ -333,7 +333,9 @@ public function addRelationship($alias, JoinPluginBase $join, $base, $link_point
    *   be tested prior to adding the table, making sure that all intermediary
    *   tables exist and are properly aliased. If set to NULL the path to
    *   the primary table will be ensured. If the path cannot be made, the
-   *   table will NOT be added.
+   *   table will NOT be added. In that case, the relationship should be added
+   *   directly with add_relationship() and the result of that should be passed
+   *   as this parameter.
    * @param \Drupal\views\Plugin\views\join\JoinPluginBase $join
    *   In some join configurations this table may actually join back through
    *   a different method; this is most likely to be used when tracing