diff --git a/src/wp-includes/option.php b/src/wp-includes/option.php
index 72f6999184..253713f4bc 100644
--- a/src/wp-includes/option.php
+++ b/src/wp-includes/option.php
@@ -844,13 +844,14 @@ function get_user_setting( $name, $default = false ) {
  * Add or update user interface setting.
  *
  * Both $name and $value can contain only ASCII letters, numbers and underscores.
+ *
  * This function has to be used before any output has started as it calls setcookie().
  *
  * @since 2.8.0
  *
  * @param string $name  The name of the setting.
  * @param string $value The value for the setting.
- * @return bool|void true if set successfully/false if not.
+ * @return bool|null True if set successfully, false if not. Null if the current user can't be established.
  */
 function set_user_setting( $name, $value ) {
 	if ( headers_sent() ) {
@@ -867,12 +868,13 @@ function set_user_setting( $name, $value ) {
  * Delete user interface settings.
  *
  * Deleting settings would reset them to the defaults.
+ *
  * This function has to be used before any output has started as it calls setcookie().
  *
  * @since 2.7.0
  *
  * @param string $names The name or array of names of the setting to be deleted.
- * @return bool|void true if deleted successfully/false if not.
+ * @return bool|null True if deleted successfully, false if not. Null if the current user can't be established.
  */
 function delete_user_setting( $names ) {
 	if ( headers_sent() ) {