diff --git a/src/Routing/PageManagerRoutes.php b/src/Routing/PageManagerRoutes.php
index eb68f65..039e83e 100644
--- a/src/Routing/PageManagerRoutes.php
+++ b/src/Routing/PageManagerRoutes.php
@@ -16,6 +16,8 @@ use Symfony\Component\Routing\RouteCollection;
 
 /**
  * Provides routes for page entities.
+ *
+ * @see \Drupal\page_manager\Entity\PageViewBuilder
  */
 class PageManagerRoutes extends RouteSubscriberBase {
 
@@ -53,12 +55,14 @@ class PageManagerRoutes extends RouteSubscriberBase {
 
       // Prepare the values that need to be altered for an existing page.
       $path = $entity->getPath();
+
       $parameters = array(
         'page_manager_page' => array(
           'type' => 'entity:page',
         ),
       );
 
+      $altered_route = FALSE;
       // Loop through all existing routes to see if this is overriding a route.
       foreach ($collection->all() as $name => $collection_route) {
         // Find all paths which match the path of the current display.
@@ -72,6 +76,8 @@ class PageManagerRoutes extends RouteSubscriberBase {
           // Merge in any route parameter definitions.
           $parameters += $collection_route->getOption('parameters') ?: array();
 
+          $altered_route = TRUE;
+
           // Update the route name this will be added to.
           $route_name = $name;
           // Remove the existing route.
@@ -80,13 +86,28 @@ class PageManagerRoutes extends RouteSubscriberBase {
         }
       }
 
+      $arguments = [];
+      // Replace % with proper route slugs ("{arg_$i}").
+      if (!$altered_route) {
+        $bits = explode('/', $path);
+        $arg_counter = 0;
+        foreach ($bits as $pos => $bit) {
+          if ($bit == '%') {
+            $arg_id = 'arg_' . $arg_counter++;
+            $arguments[$arg_id] = NULL;
+            $bits[$pos] = '{' . $arg_id . '}';
+          }
+        }
+        $path = implode("/", $bits);
+      }
+
       // Construct an add a new route.
       $route = new Route(
         $path,
         array(
           '_entity_view' => 'page_manager_page',
           'page_manager_page' => $entity_id,
-        ),
+        ) + $arguments,
         array(
           '_entity_access' => 'page_manager_page.view',
         ),
diff --git a/tests/src/Unit/PageManagerRoutesTest.php b/tests/src/Unit/PageManagerRoutesTest.php
index 6c9b2cf..36fcaf3 100644
--- a/tests/src/Unit/PageManagerRoutesTest.php
+++ b/tests/src/Unit/PageManagerRoutesTest.php
@@ -157,6 +157,54 @@ class PageManagerRoutesTest extends UnitTestCase {
   }
 
   /**
+   * Tests adding routes for an argument.
+   *
+   * @covers ::alterRoutes
+   */
+  public function testAlterRoutesWithArgument() {
+    // Set up a valid page.
+    $page1 = $this->getMock('Drupal\page_manager\PageInterface');
+    $page1->expects($this->once())
+      ->method('status')
+    ->willReturn(True);
+    $page1->expects($this->once())
+      ->method('getPath')
+      ->willReturn('/page1/%');
+    $page1->expects($this->once())
+      ->method('usesAdminTheme')
+      ->willReturn(True);
+    $pages['page1'] = $page1;
+
+    $this->pageStorage->expects($this->once())
+      ->method('loadMultiple')
+      ->will($this->returnValue($pages));
+
+    $collection = new RouteCollection();
+    $route_event = new RouteBuildEvent($collection);
+    $this->routeSubscriber->onAlterRoutes($route_event);
+
+    $this->assertSame(1, $collection->count());
+    $route = $collection->get('page_manager.page_view_page1');
+    $expected_defaults = array(
+      '_entity_view' => 'page_manager_page',
+      'page_manager_page' => 'page1',
+    );
+    $expected_requirements = array(
+      '_entity_access' => 'page_manager_page.view',
+    );
+    $expected_options = array(
+      'compiler_class' => 'Symfony\Component\Routing\RouteCompiler',
+      'parameters' => array(
+        'page_manager_page' => array(
+          'type' => 'entity:page',
+        ),
+      ),
+      '_admin_route' => TRUE,
+    );
+    $this->assertMatchingRoute($route, '/page1/{arg_0}', $expected_defaults, $expected_requirements, $expected_options);
+  }
+
+  /**
    * Tests overriding an existing route.
    *
    * @covers ::alterRoutes