diff --git a/core/modules/migrate/src/Plugin/MigrationInterface.php b/core/modules/migrate/src/Plugin/MigrationInterface.php
index 1b7668fc84e8090c97dcbec2de822e487e5c8eeb..488cc9f02b2d20cdc9591d388545ea342bfaeb5d 100644
--- a/core/modules/migrate/src/Plugin/MigrationInterface.php
+++ b/core/modules/migrate/src/Plugin/MigrationInterface.php
@@ -121,8 +121,11 @@ public function getSourcePlugin();
   /**
    * Returns the process plugins.
    *
-   * @param array $process
-   *   A process configuration array.
+   * @param array|null $process
+   *   (Optional) A process configuration array. Defaults to NULL. If specified,
+   *   then the plugins from the given process array are returned. If not
+   *   specified, then the plugins from this migration's process array are
+   *   returned.
    *
    * @return \Drupal\migrate\Plugin\MigrateProcessInterface[][]
    *   An associative array. The keys are the destination property names. Values