diff --git a/core/lib/Drupal/Component/Utility/PlaceholderTrait.php b/core/lib/Drupal/Component/Utility/PlaceholderTrait.php
index fa92b27..65c2d45 100644
--- a/core/lib/Drupal/Component/Utility/PlaceholderTrait.php
+++ b/core/lib/Drupal/Component/Utility/PlaceholderTrait.php
@@ -92,7 +92,7 @@ protected static function placeholderFormat($string, array $args) {
           break;
 
         default:
-          trigger_error('Invalid placeholder', E_USER_ERROR);
+          trigger_error('Invalid placeholder: ' . $key, E_USER_ERROR);
           break;
       }
     }
diff --git a/core/lib/Drupal/Core/Controller/TitleResolver.php b/core/lib/Drupal/Core/Controller/TitleResolver.php
index 4fe90a6..9adff8c 100644
--- a/core/lib/Drupal/Core/Controller/TitleResolver.php
+++ b/core/lib/Drupal/Core/Controller/TitleResolver.php
@@ -60,7 +60,6 @@ public function getTitle(Request $request, Route $route) {
       if (($raw_parameters = $request->attributes->get('_raw_variables'))) {
         foreach ($raw_parameters->all() as $key => $value) {
           $args['@' . $key] = $value;
-          $args['!' . $key] = $value;
           $args['%' . $key] = $value;
         }
       }
diff --git a/core/modules/aggregator/src/Tests/AggregatorTestBase.php b/core/modules/aggregator/src/Tests/AggregatorTestBase.php
index e6d5124..d5b09e5 100644
--- a/core/modules/aggregator/src/Tests/AggregatorTestBase.php
+++ b/core/modules/aggregator/src/Tests/AggregatorTestBase.php
@@ -166,7 +166,7 @@ public function getDefaultFeedItemCount() {
   public function updateFeedItems(FeedInterface $feed, $expected_count = NULL) {
     // First, let's ensure we can get to the rss xml.
     $this->drupalGet($feed->getUrl());
-    $this->assertResponse(200, format_string('!url is reachable.', array('!url' => $feed->getUrl())));
+    $this->assertResponse(200, format_string(':url is reachable.', array(':url' => $feed->getUrl())));
 
     // Attempt to access the update link directly without an access token.
     $this->drupalGet('admin/config/services/aggregator/update/' . $feed->id());