diff --git a/core/lib/Drupal/Core/EventSubscriber/EntityRouteAlterSubscriber.php b/core/lib/Drupal/Core/EventSubscriber/EntityRouteAlterSubscriber.php
index 071647a..50e13ff 100644
--- a/core/lib/Drupal/Core/EventSubscriber/EntityRouteAlterSubscriber.php
+++ b/core/lib/Drupal/Core/EventSubscriber/EntityRouteAlterSubscriber.php
@@ -62,7 +62,9 @@ public function onRoutingRouteAlterSetLatestRevision(RouteBuildEvent $event) {
       }
       $parameters = $route->getOption('parameters') ?: [];
       foreach ($parameters as &$parameter) {
-        $parameter['load_latest_revision'] = TRUE;
+        if (!isset($parameter['load_latest_revision'])) {
+          $parameter['load_latest_revision'] = TRUE;
+        }
       }
       $route->setOption('parameters', $parameters);
     }
diff --git a/core/tests/Drupal/Tests/Core/EventSubscriber/EntityRouteAlterSubscriberTest.php b/core/tests/Drupal/Tests/Core/EventSubscriber/EntityRouteAlterSubscriberTest.php
new file mode 100644
index 0000000..b85fde5
--- /dev/null
+++ b/core/tests/Drupal/Tests/Core/EventSubscriber/EntityRouteAlterSubscriberTest.php
@@ -0,0 +1,140 @@
+<?php
+
+namespace Drupal\Tests\Core\EventSubscriber;
+
+use Drupal\Core\Entity\EntityResolverManager;
+use Drupal\Core\EventSubscriber\EntityRouteAlterSubscriber;
+use Drupal\Core\Routing\RouteBuildEvent;
+use Drupal\Tests\UnitTestCase;
+use Symfony\Component\Routing\Route;
+use Symfony\Component\Routing\RouteCollection;
+
+/**
+ * @coversDefaultClass \Drupal\Core\EventSubscriber\EntityRouteAlterSubscriber
+ * @group EventSubscriber
+ */
+class EntityRouteAlterSubscriberTest extends UnitTestCase {
+
+  /**
+   * The subscriber.
+   *
+   * @var \Drupal\Core\EventSubscriber\EntityRouteAlterSubscriber
+   */
+  protected $subscriber;
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    parent::setUp();
+    $this->subscriber = new EntityRouteAlterSubscriber($this->prophesize(EntityResolverManager::class)->reveal());
+  }
+
+  /**
+   * @covers ::onRoutingRouteAlterSetLatestRevision
+   *
+   * @dataProvider latestRevisionAlterTestCases
+   */
+  public function testLatestRevisionAlter($defaults, $parameters, $expected_parameters = FALSE) {
+    $route = new Route('/foo', $defaults, [], [
+      'parameters' => $parameters,
+    ]);
+    $collection = new RouteCollection();
+    $collection->add('foo', $route);
+
+    $this->subscriber->onRoutingRouteAlterSetLatestRevision(new RouteBuildEvent($collection));
+    // If expected parameters have not been provided, assert they are unchanged.
+    $this->assertEquals($expected_parameters ?: $parameters, $route->getOption('parameters'));
+  }
+
+  /**
+   * Data provider for ::testLatestRevisionAlter.
+   */
+  public function latestRevisionAlterTestCases() {
+    return [
+      'Entity parameter not on an entity form' => [
+        [],
+        [
+          'entity_test' => [
+            'type' => 'entity:entity_test',
+          ],
+        ],
+      ],
+      'Entity parameter on an entity form' => [
+        [
+          '_entity_form' => 'entity_test.edit'
+        ],
+        [
+          'entity_test' => [
+            'type' => 'entity:entity_test',
+          ],
+        ],
+        [
+          'entity_test' => [
+            'type' => 'entity:entity_test',
+            'load_latest_revision' => TRUE,
+          ],
+        ],
+      ],
+      'Multiple entity parameters on an entity form' => [
+        [
+          '_entity_form' => 'entity_test.edit'
+        ],
+        [
+          'entity_test' => [
+            'type' => 'entity:entity_test',
+          ],
+          'node' => [
+            'type' => 'entity:node',
+          ],
+        ],
+        [
+          'entity_test' => [
+            'type' => 'entity:entity_test',
+            'load_latest_revision' => TRUE,
+          ],
+          'node' => [
+            'type' => 'entity:node',
+            'load_latest_revision' => TRUE,
+          ],
+        ],
+      ],
+      'Overriden load_latest_revision flag does not change' => [
+        [
+          '_entity_form' => 'entity_test.edit'
+        ],
+        [
+          'entity_test' => [
+            'type' => 'entity:entity_test',
+            'load_latest_revision' => FALSE,
+          ],
+        ],
+      ],
+      'Overriden load_latest_revision flag does not change with multiple parameters' => [
+        [
+          '_entity_form' => 'entity_test.edit'
+        ],
+        [
+          'entity_test' => [
+            'type' => 'entity:entity_test',
+          ],
+          'node' => [
+            'type' => 'entity:node',
+            'load_latest_revision' => FALSE,
+          ],
+        ],
+        [
+          'entity_test' => [
+            'type' => 'entity:entity_test',
+            'load_latest_revision' => TRUE,
+          ],
+          'node' => [
+            'type' => 'entity:node',
+            'load_latest_revision' => FALSE,
+          ],
+        ],
+      ],
+    ];
+  }
+
+}