diff --git a/core/lib/Drupal/Core/Extension/module.api.php b/core/lib/Drupal/Core/Extension/module.api.php
index 65e912ba564..1b2124d16c5 100644
--- a/core/lib/Drupal/Core/Extension/module.api.php
+++ b/core/lib/Drupal/Core/Extension/module.api.php
@@ -1094,11 +1094,12 @@ function hook_updater_info_alter(&$updaters) {
  *     install phase, this should only be used for version numbers, do not set
  *     it if not applicable.
  *   - description: The description of the requirement/status.
- *   - severity: The requirement's result/severity level, one of:
+ *   - severity: (optional) The requirement's result/severity level, one of:
  *     - REQUIREMENT_INFO: For info only.
  *     - REQUIREMENT_OK: The requirement is satisfied.
  *     - REQUIREMENT_WARNING: The requirement failed with a warning.
  *     - REQUIREMENT_ERROR: The requirement failed with an error.
+ *     Defaults to REQUIREMENT_OK when installing, REQUIREMENT_INFO otherwise.
  */
 function hook_requirements($phase) {
   $requirements = [];