diff --git a/core/includes/install.core.inc b/core/includes/install.core.inc
index 872ad38..a678241 100644
--- a/core/includes/install.core.inc
+++ b/core/includes/install.core.inc
@@ -1785,7 +1785,7 @@ function _install_module_batch($module, $module_name, &$context) {
  * @param string $server_pattern
  *   Server access pattern (to replace language code, version number, etc. in).
  *
- * @return array
+ * @return array|null
  *   Requirements compliance array. If the translation was downloaded
  *   successfully then an empty array is returned. Otherwise the requirements
  *   error with detailed information.
diff --git a/core/lib/Drupal/Component/Datetime/DateTimePlus.php b/core/lib/Drupal/Component/Datetime/DateTimePlus.php
index 377bb27..8791c52 100644
--- a/core/lib/Drupal/Component/Datetime/DateTimePlus.php
+++ b/core/lib/Drupal/Component/Datetime/DateTimePlus.php
@@ -624,8 +624,9 @@ public static function datePad($value, $size = 2) {
    *   - timezone: (optional) String timezone name. Defaults to the timezone
    *     of the date object.
    *
-   * @return string
-   *   The formatted value of the date.
+   * @return string|null
+   *   The formatted value of the date or NULL if there were construction
+   *   errors.
    */
   public function format($format, $settings = array()) {
 
diff --git a/core/lib/Drupal/Core/Entity/EntityListBuilder.php b/core/lib/Drupal/Core/Entity/EntityListBuilder.php
index b9c8db3..5bfbecf 100644
--- a/core/lib/Drupal/Core/Entity/EntityListBuilder.php
+++ b/core/lib/Drupal/Core/Entity/EntityListBuilder.php
@@ -242,9 +242,6 @@ public function render() {
 
   /**
    * Gets the title of the page.
-   *
-   * @return string
-   *   A string title of the page.
    */
   protected function getTitle() {
     return;
diff --git a/core/modules/dblog/src/Controller/DbLogController.php b/core/modules/dblog/src/Controller/DbLogController.php
index 7c83cce..6aad7a0 100644
--- a/core/modules/dblog/src/Controller/DbLogController.php
+++ b/core/modules/dblog/src/Controller/DbLogController.php
@@ -299,8 +299,9 @@ public function eventDetails($event_id) {
   /**
    * Builds a query for database log administration filters based on session.
    *
-   * @return array
-   *   An associative array with keys 'where' and 'args'.
+   * @return array|null
+   *   An associative array with keys 'where' and 'args' or NULL if there were
+   *   no filters set.
    */
   protected function buildFilterQuery() {
     if (empty($_SESSION['dblog_overview_filter'])) {
diff --git a/core/modules/forum/src/Tests/ForumTest.php b/core/modules/forum/src/Tests/ForumTest.php
index 1327714..6bb66ca 100644
--- a/core/modules/forum/src/Tests/ForumTest.php
+++ b/core/modules/forum/src/Tests/ForumTest.php
@@ -521,8 +521,8 @@ function testForumWithNewPost() {
    * @param bool $container
    *   TRUE if $forum is a container; FALSE otherwise.
    *
-   * @return object
-   *   The created topic node.
+   * @return object|null
+   *   The created topic node or NULL if there were errors.
    */
   function createForumTopic($forum, $container = FALSE) {
     // Generate a random subject/body.
diff --git a/core/modules/simpletest/simpletest.module b/core/modules/simpletest/simpletest.module
index d119f7f..c5b8908 100644
--- a/core/modules/simpletest/simpletest.module
+++ b/core/modules/simpletest/simpletest.module
@@ -689,9 +689,10 @@ function simpletest_mail_alter(&$message) {
  * @param $phpunit_xml_file
  *   Path to the PHPUnit XML file.
  *
- * @return array[]
+ * @return array[]|null
  *   The results as array of rows in a format that can be inserted into
- *   {simpletest}.
+ *   {simpletest}. If the phpunit_xml_file does not have any contents then the
+ *   function will return NULL.
  */
 function simpletest_phpunit_xml_to_rows($test_id, $phpunit_xml_file) {
   $contents = @file_get_contents($phpunit_xml_file);
diff --git a/core/modules/system/src/Tests/Module/ModuleTestBase.php b/core/modules/system/src/Tests/Module/ModuleTestBase.php
index e212617..81c4f12 100644
--- a/core/modules/system/src/Tests/Module/ModuleTestBase.php
+++ b/core/modules/system/src/Tests/Module/ModuleTestBase.php
@@ -87,8 +87,9 @@ function assertModuleTablesDoNotExist($module) {
    * @param string $module
    *   The name of the module.
    *
-   * @return bool
-   *   TRUE if configuration has been installed, FALSE otherwise.
+   * @return bool|NULL
+   *   TRUE if configuration has been installed, FALSE otherwise. Returns NULL
+   *   if the module configuration directory does not exist.
    */
   function assertModuleConfig($module) {
     $module_config_dir = drupal_get_path('module', $module) . '/' . InstallStorage::CONFIG_INSTALL_DIRECTORY;
diff --git a/core/phpcs.xml.dist b/core/phpcs.xml.dist
index 0ac6cec..dab6a29 100644
--- a/core/phpcs.xml.dist
+++ b/core/phpcs.xml.dist
@@ -47,7 +47,6 @@
     <exclude name="Drupal.Commenting.FunctionComment.IncorrectTypeHint"/>
     <exclude name="Drupal.Commenting.FunctionComment.InvalidNoReturn"/>
     <exclude name="Drupal.Commenting.FunctionComment.InvalidReturn"/>
-    <exclude name="Drupal.Commenting.FunctionComment.InvalidReturnNotVoid"/>
     <exclude name="Drupal.Commenting.FunctionComment.InvalidTypeHint"/>
     <exclude name="Drupal.Commenting.FunctionComment.Missing"/>
     <exclude name="Drupal.Commenting.FunctionComment.MissingFile"/>