diff --git a/page_manager_ui/src/Entity/PageListBuilder.php b/page_manager_ui/src/Entity/PageListBuilder.php
index a1bb281..92abedc 100644
--- a/page_manager_ui/src/Entity/PageListBuilder.php
+++ b/page_manager_ui/src/Entity/PageListBuilder.php
@@ -52,7 +52,7 @@ protected function getPath(PageInterface $entity) {
     // If the page is enabled and not dynamic, show the path as a link,
     // otherwise as plain text.
     $path = $entity->getPath();
-    if ($entity->status() && strpos($path, '%') === FALSE) {
+    if ($entity->status() && strpos($path, '{') === FALSE) {
       return [
         'data' => [
           '#type' => 'link',
diff --git a/page_manager_ui/src/Form/PageFormBase.php b/page_manager_ui/src/Form/PageFormBase.php
index e5c17a8..d089b5e 100644
--- a/page_manager_ui/src/Form/PageFormBase.php
+++ b/page_manager_ui/src/Form/PageFormBase.php
@@ -107,6 +107,13 @@ public function validatePath(&$element, FormStateInterface $form_state) {
     $value = '/' . trim($element['#value'], '/');
     $form_state->setValueForElement($element, $value);
 
+    if (strpos($value, '%')) {
+      $form_state->setErrorByName('path', 'The entity path may not contain "%".');
+    }
+    if ($value === '/') {
+      $form_state->setErrorByName('path', 'The entity path may not be "/".');
+    }
+
     // Ensure each path is unique.
     $path = $this->entityQuery->get('page')
       ->condition('path', $value)
diff --git a/page_manager_ui/src/Tests/PageManagerAdminTest.php b/page_manager_ui/src/Tests/PageManagerAdminTest.php
index 9811fd6..6fa0159 100644
--- a/page_manager_ui/src/Tests/PageManagerAdminTest.php
+++ b/page_manager_ui/src/Tests/PageManagerAdminTest.php
@@ -59,6 +59,8 @@ public function testAdmin() {
     $this->doTestEditVariant();
     $this->doTestReorderVariants();
     $this->doTestAddPageWithDuplicatePath();
+    $this->doTestAddPageWithSlashOnlyPath();
+    $this->doTestAddPageWithPercentInPath();
     $this->doTestAdminPath();
     $this->doTestRemoveVariant();
     $this->doTestRemoveBlock();
@@ -355,6 +357,38 @@ protected function doTestAddPageWithDuplicatePath() {
   }
 
   /**
+   * Tests adding a page with a path of "/".
+   */
+  protected function doTestAddPageWithSlashOnlyPath() {
+    // Try to add a second page with the same path.
+    $edit = [
+      'label' => 'Bar',
+      'id' => 'bar',
+      'path' => '/',
+    ];
+    $this->drupalPostForm('admin/structure/page_manager/add', $edit, 'Save');
+    $this->assertText('The entity path may not be "/".');
+    $this->drupalGet('admin/structure/page_manager');
+    $this->assertNoText('Bar');
+  }
+
+  /**
+   * Tests adding a page with a path containing "%".
+   */
+  protected function doTestAddPageWithPercentInPath() {
+    // Try to add a second page with the same path.
+    $edit = [
+      'label' => 'Bar',
+      'id' => 'bar',
+      'path' => 'admin/%',
+    ];
+    $this->drupalPostForm('admin/structure/page_manager/add', $edit, 'Save');
+    $this->assertText('The entity path may not contain "%".');
+    $this->drupalGet('admin/structure/page_manager');
+    $this->assertNoText('Bar');
+  }
+
+  /**
    * Tests changing the admin theme of a page.
    */
   protected function doTestAdminPath() {
diff --git a/src/Routing/PageManagerRoutes.php b/src/Routing/PageManagerRoutes.php
index 793d3c8..92897c6 100644
--- a/src/Routing/PageManagerRoutes.php
+++ b/src/Routing/PageManagerRoutes.php
@@ -9,7 +9,6 @@
 
 use Drupal\Core\Cache\CacheTagsInvalidatorInterface;
 use Drupal\Core\Entity\EntityTypeManagerInterface;
-use Drupal\Core\Routing\RouteCompiler;
 use Drupal\Core\Routing\RouteSubscriberBase;
 use Drupal\Core\Routing\RoutingEvents;
 use Drupal\page_manager\PageInterface;
@@ -60,6 +59,14 @@ protected function alterRoutes(RouteCollection $collection) {
         continue;
       }
 
+      $path = $entity->getPath();
+      if (strpos($path, '%')) {
+        throw new \UnexpectedValueException('The entity path may not contain "%"');
+      }
+      if ($path === '/') {
+        throw new \UnexpectedValueException('The entity path may not be "/"');
+      }
+
       $parameters = [];
       $requirements = [];
       if ($route_name = $this->findPageRouteName($entity, $collection)) {
@@ -74,7 +81,6 @@ protected function alterRoutes(RouteCollection $collection) {
       }
       else {
         $route_name = "page_manager.page_view_$entity_id";
-        $path = $entity->getPath();
       }
 
       // Add in configured parameters.
@@ -135,11 +141,7 @@ protected function findPageRouteName(PageInterface $entity, RouteCollection $col
     // Loop through all existing routes to see if this is overriding a route.
     foreach ($collection->all() as $name => $collection_route) {
       // Find all paths which match the path of the current display.
-      $route_path = $collection_route->getPath();
-      $route_path_outline = RouteCompiler::getPatternOutline($route_path);
-
-      // Match either the path or the outline, e.g., '/foo/{foo}' or '/foo/%'.
-      if ($path === $route_path || $path === $route_path_outline) {
+      if ($path === $collection_route->getPath()) {
         // Return the overridden route name.
         return $name;
       }
diff --git a/src/Tests/PagePlaceholderTest.php b/src/Tests/PagePlaceholderTest.php
index 9f940e3..a2ef1e2 100644
--- a/src/Tests/PagePlaceholderTest.php
+++ b/src/Tests/PagePlaceholderTest.php
@@ -48,7 +48,7 @@ public function testPagePlaceHolder() {
     $page = Page::create([
       'label' => 'Placeholder test',
       'id' => 'placeholder',
-      'path' => '/page-manager-test/%',
+      'path' => '/page-manager-test/{page}',
     ]);
     $page->save();
 
diff --git a/tests/src/Unit/PageManagerRoutesTest.php b/tests/src/Unit/PageManagerRoutesTest.php
index fe6f005..4ce98e0 100644
--- a/tests/src/Unit/PageManagerRoutesTest.php
+++ b/tests/src/Unit/PageManagerRoutesTest.php
@@ -72,6 +72,50 @@ protected function setUp() {
   }
 
   /**
+   * Tests adding a route with an invalid '%' placeholder.
+   *
+   * @covers ::alterRoutes
+   *
+   * @expectedException \UnexpectedValueException
+   * @expectedExceptionMessage The entity path may not contain "%"
+   */
+  public function testAlterRoutesWithPercentPlaceholder() {
+    /** @var \Drupal\page_manager\PageInterface|\Prophecy\Prophecy\ProphecyInterface $page */
+    $page = $this->prophesize(PageInterface::class);
+    $page->status()->willReturn(TRUE);
+    $page->getPath()->willReturn('/path/with/%')->shouldBeCalled();
+
+    $variant = $this->prophesize(PageVariantInterface::class);
+    $page->getVariants()->willReturn(['variant' => $variant->reveal()]);
+
+    $this->pageStorage->loadMultiple()->willReturn(['page' => $page->reveal()]);
+
+    $this->routeSubscriber->onAlterRoutes(new RouteBuildEvent(new RouteCollection()));
+  }
+
+  /**
+   * Tests adding a route with a path of '/'.
+   *
+   * @covers ::alterRoutes
+   *
+   * @expectedException \UnexpectedValueException
+   * @expectedExceptionMessage The entity path may not be "/"
+   */
+  public function testAlterRoutesWithOnlySlash() {
+    /** @var \Drupal\page_manager\PageInterface|\Prophecy\Prophecy\ProphecyInterface $page */
+    $page = $this->prophesize(PageInterface::class);
+    $page->status()->willReturn(TRUE);
+    $page->getPath()->willReturn('/')->shouldBeCalled();
+
+    $variant = $this->prophesize(PageVariantInterface::class);
+    $page->getVariants()->willReturn(['variant' => $variant->reveal()]);
+
+    $this->pageStorage->loadMultiple()->willReturn(['page' => $page->reveal()]);
+
+    $this->routeSubscriber->onAlterRoutes(new RouteBuildEvent(new RouteCollection()));
+  }
+
+  /**
    * Tests adding routes for enabled and disabled pages.
    *
    * @covers ::alterRoutes
@@ -230,9 +274,7 @@ public function providerTestAlterRoutesOverrideExisting() {
     $data = [];
     $data['no_slug'] = ['/test_route', '/test_route'];
     $data['slug'] = ['/test_route/{test_route}', '/test_route/{test_route}'];
-    $data['placeholder'] = ['/test_route/%', '/test_route/{test_route}'];
     $data['slug_with_default'] = ['/test_route/{default_exists}', '/test_route/{default_exists}'];
-    $data['placeholder_with_default'] = ['/test_route/%', '/test_route/{default_exists}'];
     $data['with_requirement'] = ['/test_route/{foo}', '/test_route/{foo}', ['foo' => '\d+']];
     return $data;
   }