diff --git a/core/modules/system/system.admin.inc b/core/modules/system/system.admin.inc
index b194619..77f5a75 100644
--- a/core/modules/system/system.admin.inc
+++ b/core/modules/system/system.admin.inc
@@ -1775,6 +1775,9 @@ function system_file_system_settings() {
 /**
  * Form validation handler for the system_file_system_settings() form.
  *
+ * Validates that the private and temporary directories do not resolve to the
+ * same location as the public directory.
+ *
  * @see system_file_system_settings_submit()
  */
 function system_file_system_settings_validate($form, &$form_state) {