diff --git a/core/lib/Drupal/Component/Utility/Crypt.php b/core/lib/Drupal/Component/Utility/Crypt.php
index 73acc4e10967069a5accfa386960793e276f953b..00a036705576c26aba5471c9212eb61761ac7941 100644
--- a/core/lib/Drupal/Component/Utility/Crypt.php
+++ b/core/lib/Drupal/Component/Utility/Crypt.php
@@ -108,7 +108,8 @@ public static function hashEquals($known_string, $user_string) {
    *   The number of random bytes to fetch and base64 encode.
    *
    * @return string
-   *   The base64 encoded result will have a length of up to 4 * $count.
+   *   A base-64 encoded string, with + replaced with -, / with _ and any =
+   *   padding characters removed.
    *
    * @see \Drupal\Component\Utility\Crypt::randomBytes()
    */