diff --git a/page_manager/src/Routing/PageManagerRoutes.php b/page_manager/src/Routing/PageManagerRoutes.php
index cb15649376..dca84f1eab 100644
--- a/page_manager/src/Routing/PageManagerRoutes.php
+++ b/page_manager/src/Routing/PageManagerRoutes.php
@@ -66,7 +66,7 @@ protected function alterRoutes(RouteCollection $collection) {
         $collection_route = $collection->get($overridden_route_name);
 
         // Add the name of the overridden route for use during filtering.
-        $defaults['overridden_route_name'] = $overridden_route_name;
+        $defaults['_overridden_route_name'] = $overridden_route_name;
         $path = $collection_route->getPath();
         $parameters = $collection_route->getOption('parameters') ?: [];
         $requirements = $collection_route->getRequirements();
diff --git a/page_manager/tests/src/Unit/PageManagerRoutesTest.php b/page_manager/tests/src/Unit/PageManagerRoutesTest.php
index c092afefa0..30dbd036dc 100644
--- a/page_manager/tests/src/Unit/PageManagerRoutesTest.php
+++ b/page_manager/tests/src/Unit/PageManagerRoutesTest.php
@@ -208,7 +208,7 @@ public function testAlterRoutesOverrideExisting($page_path, $existing_route_path
       'page_manager_page_variant' => 'variant1',
       'page_manager_page' => 'page1',
       'page_manager_page_variant_weight' => 0,
-      'overridden_route_name' => 'test_route',
+      '_overridden_route_name' => 'test_route',
       'base_route_name' => 'test_route',
     ];
     $expected_requirements = $requirements + ['_page_access' => 'page_manager_page.view'];
@@ -311,7 +311,7 @@ public function testAlterRoutesMultipleVariantsDifferentRequirements() {
           'page_manager_page_variant' => 'variant1',
           'page_manager_page' => 'page1',
           'page_manager_page_variant_weight' => 0,
-          'overridden_route_name' => 'test_route',
+          '_overridden_route_name' => 'test_route',
           'base_route_name' => 'test_route',
         ],
         'requirements' => [
@@ -411,7 +411,7 @@ public function testAlterRoutesOverrideExistingWithConfiguredParameters($page_pa
       'page_manager_page_variant' => 'variant1',
       'page_manager_page' => 'page1',
       'page_manager_page_variant_weight' => 0,
-      'overridden_route_name' => $route_name,
+      '_overridden_route_name' => $route_name,
       'base_route_name' => 'test_route',
     ];
     $expected_requirements = $requirements + ['_page_access' => 'page_manager_page.view'];