diff --git a/core/includes/form.inc b/core/includes/form.inc
index 39ae1e2cf6..bacab5ef71 100644
--- a/core/includes/form.inc
+++ b/core/includes/form.inc
@@ -73,12 +73,12 @@ function form_select_options($element, $choices = NULL) {
     }
     $choices = $element['#options'];
     $sort_options = isset($element['#sort_options']) && $element['#sort_options'];
-    $sort_start = isset($element['#sort_start']) ? $element['#sort_start'] : 0;
+    $sort_start = $element['#sort_start'] ?? 0;
   }
   else {
     // We are within an option group.
     $sort_options = isset($choices['#sort_options']) && $choices['#sort_options'];
-    $sort_start = isset($choices['#sort_start']) ? $choices['#sort_start'] : 0;
+    $sort_start = $choices['#sort_start'] ?? 0;
     unset($choices['#sort_options']);
     unset($choices['#sort_start']);
   }
diff --git a/core/lib/Drupal/Core/Render/Element/Select.php b/core/lib/Drupal/Core/Render/Element/Select.php
index 342b763f6e..7394614bb9 100644
--- a/core/lib/Drupal/Core/Render/Element/Select.php
+++ b/core/lib/Drupal/Core/Render/Element/Select.php
@@ -31,10 +31,10 @@
  *   options by their labels, after rendering and translation is complete.
  *   Can be set within an option group to sort that group.
  * - #sort_start: (optional) Option index to start sorting at, where 0 is the
- *   first option (default is 0, and this only applies if #sort_options is
- *   TRUE). Can be used within an option group. If an empty option is being
- *   added automatically (see #empty_option and #empty_value properties), and
- *   you want it to stay at the top of the list, be sure to start sorting at 1.
+ *   first option. Can be used within an option group. If an empty option is
+ *   being added automatically (see #empty_option and #empty_value properties),
+ *   this defaults to 1 to keep the empty option at the top of the list.
+ *   Otherwise, it defaults to 0.
  * - #empty_option: (optional) The label to show for the first default option.
  *   By default, the label is automatically set to "- Select -" for a required
  *   field and "- None -" for an optional field.
@@ -90,7 +90,7 @@ public function getInfo() {
       '#input' => TRUE,
       '#multiple' => FALSE,
       '#sort_options' => FALSE,
-      '#sort_start' => 0,
+      '#sort_start' => NULL,
       '#process' => [
         [$class, 'processSelect'],
         [$class, 'processAjaxForm'],
@@ -152,6 +152,9 @@ public static function processSelect(&$element, FormStateInterface $form_state,
         $element['#options'] = $empty_option + $element['#options'];
       }
     }
+    // Provide the correct default value for #sort_start.
+    $element['#sort_start'] = $element['#sort_start'] ??
+      ((isset($element['#empty_value'])) ? 1 : 0);
     return $element;
   }
 
diff --git a/core/modules/system/tests/modules/form_test/src/Form/FormTestSelectForm.php b/core/modules/system/tests/modules/form_test/src/Form/FormTestSelectForm.php
index e4ab781468..cd8542c68e 100644
--- a/core/modules/system/tests/modules/form_test/src/Form/FormTestSelectForm.php
+++ b/core/modules/system/tests/modules/form_test/src/Form/FormTestSelectForm.php
@@ -133,7 +133,8 @@ public function buildForm(array $form, FormStateInterface $form_state) {
     ];
 
     // Add a select to test sorting at the top level, and with some of the
-    // option groups sorted and some left alone.
+    // option groups sorted, some left alone, and at least one with sort start
+    // set to a non-default value.
     $sortable_options = $this->makeSortableOptions('sso');
     $sortable_options['sso_zzgroup']['#sort_options'] = TRUE;
     $sortable_options['sso_xxgroup']['#sort_options'] = TRUE;
@@ -157,6 +158,17 @@ public function buildForm(array $form, FormStateInterface $form_state) {
       '#empty_value' => 'sno_empty',
     ];
 
+    // Add a select to test sorting with a -NONE- option included,
+    // and sort start not set.
+    $sortable_none_nostart_options = $this->makeSortableOptions('snn');
+    $sortable_none_nostart_options['snn_zzgroup']['#sort_options'] = TRUE;
+    $form['sorted_none_nostart'] = [
+      '#type' => 'select',
+      '#options' => $sortable_none_nostart_options,
+      '#sort_options' => TRUE,
+      '#empty_value' => 'snn_empty',
+    ];
+
     $form['submit'] = ['#type' => 'submit', '#value' => 'Submit'];
     return $form;
   }
@@ -172,9 +184,9 @@ public function buildForm(array $form, FormStateInterface $form_state) {
    */
   protected function makeSortableOptions($prefix) {
     return [
-      // Don't use $this->t() here, because we really don't want these
-      // to be translated or added to localize.d.o. Using TranslatableMarkup
-      // in places tests that casting to string is working, however.
+      // Don't use $this->t() here, to avoid adding strings to
+      // localize.drupal.org. Do use TranslatableMarkup in places, to test
+      // that labels are cast to strings before sorting.
       $prefix . '_first_element' => new TranslatableMarkup('first element'),
       $prefix . '_second' => new TranslatableMarkup('second element'),
       $prefix . '_zzgroup' => [
diff --git a/core/modules/system/tests/src/Functional/Form/FormTest.php b/core/modules/system/tests/src/Functional/Form/FormTest.php
index 7df29f31ae..0551c88322 100644
--- a/core/modules/system/tests/src/Functional/Form/FormTest.php
+++ b/core/modules/system/tests/src/Functional/Form/FormTest.php
@@ -535,6 +535,28 @@ public function testSelectSorting() {
       'sno_gf',
     ]);
 
+    $this->validateSelectSorting('sorted_none_nostart', [
+      'snn_empty',
+      'snn_a',
+      'snn_d',
+      'snn_first_element',
+      'snn_b',
+      'snn_c',
+      'snn_second',
+      'snn_xxgroup',
+      'snn_gz',
+      'snn_gi',
+      'snn_gh',
+      'snn_yygroup',
+      'snn_ge',
+      'snn_gd',
+      'snn_gf',
+      'snn_zzgroup',
+      'snn_ga',
+      'snn_gb',
+      'snn_gc',
+    ]);
+
     // Verify that #sort_order and #sort_start are not in the page.
     $this->assertSession()->responseNotContains('#sort_order');
     $this->assertSession()->responseNotContains('#sort_start');