diff --git a/core/lib/Drupal/Core/Form/DialogFormTrait.php b/core/lib/Drupal/Core/Form/DialogFormTrait.php
index 145a34ecfa..3d4d884a50 100644
--- a/core/lib/Drupal/Core/Form/DialogFormTrait.php
+++ b/core/lib/Drupal/Core/Form/DialogFormTrait.php
@@ -21,11 +21,16 @@
    *   An associative array containing the structure of the form.
    * @param \Drupal\Core\Form\FormStateInterface $form_state
    *   The current state of the form.
+   * @param bool $create_cancel
+   *   If TRUE the create submit button will be created.
+   * @param string $dialog_selector
+   *   The CSS selector for the associated dialog.
    */
-  protected function buildFormDialog(array &$form, FormStateInterface $form_state, $create_cancel = FALSE) {
+  protected function buildFormDialog(array &$form, FormStateInterface $form_state, $create_cancel = FALSE, $dialog_selector = '#drupal-modal') {
     if (!$this->isDialog()) {
       return;
     }
+    $form_state->set('dialog_selector', $dialog_selector);
 
     $ajax_callback_added = FALSE;
 
@@ -138,7 +143,8 @@ public function submitFormDialog(array &$form, FormStateInterface $form_state) {
    *   An AJAX response that display validation error messages.
    */
   public function closeDialog(array &$form, FormStateInterface $form_state) {
-    return (new AjaxResponse())->addCommand(new CloseDialogCommand($this->getDialogSelector()));
+    $selector = $form_state->get('dialog_selector');
+    return (new AjaxResponse())->addCommand(new CloseDialogCommand($selector));
   }
 
   /**
@@ -190,16 +196,4 @@ protected function getRedirectDestinationPath() {
     }
   }
 
-  /**
-   * @return string
-   */
-  protected function getDialogSelector() {
-    if ($this->getRequestWrapperFormat() === 'drupal_dialog.off_canvas') {
-      return '#drupal-off-canvas';
-    }
-    else {
-      return '#drupal-modal';
-    }
-  }
-
 }
diff --git a/core/modules/outside_in/src/Block/BlockEntityOffCanvasForm.php b/core/modules/outside_in/src/Block/BlockEntityOffCanvasForm.php
index 58d287fed8..063a2ea87d 100644
--- a/core/modules/outside_in/src/Block/BlockEntityOffCanvasForm.php
+++ b/core/modules/outside_in/src/Block/BlockEntityOffCanvasForm.php
@@ -128,7 +128,7 @@ public function submitForm(array &$form, FormStateInterface $form_state) {
    */
   public function buildForm(array $form, FormStateInterface $form_state) {
     $form = parent::buildForm($form, $form_state);
-    $this->buildFormDialog($form, $form_state);
+    $this->buildFormDialog($form, $form_state, FALSE, '#drupal-off-canvas');
     return $form;
   }
 
diff --git a/core/modules/outside_in/tests/modules/off_canvas_test/src/Form/TestForm.php b/core/modules/outside_in/tests/modules/off_canvas_test/src/Form/TestForm.php
index 64b14e8e6c..3812e40ca9 100644
--- a/core/modules/outside_in/tests/modules/off_canvas_test/src/Form/TestForm.php
+++ b/core/modules/outside_in/tests/modules/off_canvas_test/src/Form/TestForm.php
@@ -39,7 +39,7 @@ public function buildForm(array $form, FormStateInterface $form_state) {
         '#value' => $this->t('Cancel'),
       ],
     ];
-    $this->buildFormDialog($form, $form_state);
+    $this->buildFormDialog($form, $form_state, FALSE, '#drupal-off-canvas');
     return $form;
   }