diff -u b/core/lib/Drupal/Core/Extension/ModuleHandler.php b/core/lib/Drupal/Core/Extension/ModuleHandler.php
--- b/core/lib/Drupal/Core/Extension/ModuleHandler.php
+++ b/core/lib/Drupal/Core/Extension/ModuleHandler.php
@@ -639,8 +639,7 @@
    * @return
    *   An associative array with either three or four keys:
    *   - name: The name of the thing to depend on (e.g. 'foo').
-   *   - project: (optional) The name of the project that contains
-   *     the thing to depend on.
+   *   - project: The name of the project that contains the thing to depend on.
    *   - original_version: The original version string (which can be
    *     used in the UI for reporting incompatibilities).
    *   - versions: List of associative arrays, each containing the keys