diff --git a/core/lib/Drupal/Core/FileTransfer/Form/FileTransferAuthorizeForm.php b/core/lib/Drupal/Core/FileTransfer/Form/FileTransferAuthorizeForm.php
index 9034f0771a..86e6221535 100644
--- a/core/lib/Drupal/Core/FileTransfer/Form/FileTransferAuthorizeForm.php
+++ b/core/lib/Drupal/Core/FileTransfer/Form/FileTransferAuthorizeForm.php
@@ -51,12 +51,11 @@ public function getFormId() {
    */
   public function buildForm(array $form, FormStateInterface $form_state) {
     // Get all the available ways to transfer files.
-    $request = $this->getRequest();
-    if (!$request->getSession()->has('authorize_filetransfer_info')) {
+    $available_backends = $this->getRequest()->getSession()->get('authorize_filetransfer_info', []);
+    if (empty($available_backends)) {
       drupal_set_message($this->t('Unable to continue, no available methods of file transfer'), 'error');
       return [];
     }
-    $available_backends = $request->getSession()->get('authorize_filetransfer_info');
 
     if (!$this->getRequest()->isSecure()) {
       $form['information']['https_warning'] = [
diff --git a/core/modules/dblog/src/Controller/DbLogController.php b/core/modules/dblog/src/Controller/DbLogController.php
index a049737056..a60c3fd574 100644
--- a/core/modules/dblog/src/Controller/DbLogController.php
+++ b/core/modules/dblog/src/Controller/DbLogController.php
@@ -323,7 +323,7 @@ protected function buildFilterQuery(Request $request) {
 
     // Build query.
     $where = $args = [];
-    foreach ($request->getSession()->get('dblog_overview_filter') as $key => $filter) {
+    foreach ($request->getSession()->get('dblog_overview_filter', []) as $key => $filter) {
       $filter_where = [];
       foreach ($filter as $value) {
         $filter_where[] = $filters[$key]['where'];
diff --git a/core/modules/dblog/src/Form/DblogFilterForm.php b/core/modules/dblog/src/Form/DblogFilterForm.php
index 6c06c23606..08b7f24e41 100644
--- a/core/modules/dblog/src/Form/DblogFilterForm.php
+++ b/core/modules/dblog/src/Form/DblogFilterForm.php
@@ -30,7 +30,7 @@ public function buildForm(array $form, FormStateInterface $form_state) {
       '#title' => $this->t('Filter log messages'),
       '#open' => TRUE,
     ];
-    $session_filters = $this->getRequest()->getSession()->get('dblog_overview_filter');
+    $session_filters = $this->getRequest()->getSession()->get('dblog_overview_filter', []);
     foreach ($filters as $key => $filter) {
       $form['filters']['status'][$key] = [
         '#title' => $filter['title'],
diff --git a/core/modules/system/tests/modules/session_test/src/Controller/SessionTestController.php b/core/modules/system/tests/modules/session_test/src/Controller/SessionTestController.php
index 9a54b8af94..7ae40bb3d5 100644
--- a/core/modules/system/tests/modules/session_test/src/Controller/SessionTestController.php
+++ b/core/modules/system/tests/modules/session_test/src/Controller/SessionTestController.php
@@ -138,9 +138,8 @@ public function isLoggedIn() {
    */
   public function traceHandler(Request $request) {
     $session = $request->getSession();
-    // Start a session if necessary, set a value and then save and close it.
-    $session->start();
     $session->set('trace-handler', $session->get('trace-handler', 0) + 1);
+    // Close the session to create the trace.
     $request->getSession()->save();
 
     // Collect traces and return them in JSON format.