diff --git a/core/modules/outside_in/outside_in.links.contextual.yml b/core/modules/outside_in/outside_in.links.contextual.yml
index ee83136..05455f3 100644
--- a/core/modules/outside_in/outside_in.links.contextual.yml
+++ b/core/modules/outside_in/outside_in.links.contextual.yml
@@ -1,4 +1,4 @@
 outside_in.block_configure:
   title: 'Quick Edit'
-  route_name: 'entity.block.edit_form'
+  route_name: 'entity.block.offcanvas_form'
   group: 'block'
diff --git a/core/modules/outside_in/src/Block/BlockEntityOffcanvasForm.php b/core/modules/outside_in/src/Block/BlockEntityOffcanvasForm.php
index 210b9e5..2c5ad58 100644
--- a/core/modules/outside_in/src/Block/BlockEntityOffcanvasForm.php
+++ b/core/modules/outside_in/src/Block/BlockEntityOffcanvasForm.php
@@ -70,7 +70,7 @@ public function form(array $form, FormStateInterface $form_state) {
     $form['#tree'] = TRUE;
     $form['#attached']['library'][] = 'block/drupal.block.admin';
 
-    $form['settings'] = $this->blockManager->getFormObject($this->entity->getPlugin(), 'sidebar')->buildConfigurationForm([], $form_state);
+    $form['settings'] = $this->blockManager->getFormObject($this->entity->getPlugin(), 'offcavnas')->buildConfigurationForm([], $form_state);
 
     return $form;
   }
diff --git a/core/modules/outside_in/src/Block/OutsideInBlockManager.php b/core/modules/outside_in/src/Block/OutsideInBlockManager.php
index f335d79..474f8a0 100644
--- a/core/modules/outside_in/src/Block/OutsideInBlockManager.php
+++ b/core/modules/outside_in/src/Block/OutsideInBlockManager.php
@@ -34,8 +34,15 @@ public function __construct(ClassResolverInterface $class_resolver) {
    */
   public function getFormObject(PluginInspectionInterface $plugin, $operation) {
     $definition = $plugin->getPluginDefinition();
+
     if (!isset($definition['form'][$operation])) {
-      throw new InvalidPluginDefinitionException($plugin->getPluginId(), sprintf('The "%s" plugin did not specify a "%s" form class', $plugin->getPluginId(), $operation));
+      // Use the default form class if no form is specified for this operation.
+      if (isset($definition['form']['default'])) {
+        $operation = 'default';
+      }
+      else {
+        throw new InvalidPluginDefinitionException($plugin->getPluginId(), sprintf('The "%s" plugin did not specify a "%s" form class', $plugin->getPluginId(), $operation));
+      }
     }
 
     // If the form specified is the plugin itself, use it directly.
diff --git a/core/modules/outside_in/tests/modules/offcanvas_test/src/Form/OffcanvasForm.php b/core/modules/outside_in/tests/modules/offcanvas_test/src/Form/OffCanvasForm.php
similarity index 100%
rename from core/modules/outside_in/tests/modules/offcanvas_test/src/Form/OffcanvasForm.php
rename to core/modules/outside_in/tests/modules/offcanvas_test/src/Form/OffCanvasForm.php
diff --git a/core/modules/outside_in/tests/src/Unit/OutsideInBlockManagerTest.php b/core/modules/outside_in/tests/src/Unit/OutsideInBlockManagerTest.php
index d0f3ccc..1158516 100644
--- a/core/modules/outside_in/tests/src/Unit/OutsideInBlockManagerTest.php
+++ b/core/modules/outside_in/tests/src/Unit/OutsideInBlockManagerTest.php
@@ -81,6 +81,23 @@ public function testGetFormObjectUsingPlugin() {
   /**
    * @covers ::getFormObject
    */
+  public function testGetFormObjectDefaultFallback() {
+    $this->classResolver->getInstanceFromDefinition(Argument::cetera())->shouldNotBeCalled();
+
+    $plugin = $this->prophesize(PluginInspectionInterface::class)->willImplement(PluginFormInterface::class);
+    $plugin->getPluginDefinition()->willReturn([
+      'form' => [
+        'default' => get_class($plugin->reveal()),
+      ],
+    ]);
+
+    $form_object = $this->manager->getFormObject($plugin->reveal(), 'missing');
+    $this->assertSame($plugin->reveal(), $form_object);
+  }
+
+  /**
+   * @covers ::getFormObject
+   */
   public function testGetFormObjectOperationAware() {
     $plugin_form = $this->prophesize(PluginFormInterface::class)->willImplement(OperationAwareFormInterface::class);
     $plugin_form->setOperation('operation_aware')->shouldBeCalled();