diff --git a/core/modules/system/src/Tests/Bootstrap/DrupalSetMessageTest.php b/core/modules/system/src/Tests/Bootstrap/DrupalSetMessageTest.php
index 4c4ce60..394c0b2 100644
--- a/core/modules/system/src/Tests/Bootstrap/DrupalSetMessageTest.php
+++ b/core/modules/system/src/Tests/Bootstrap/DrupalSetMessageTest.php
@@ -55,8 +55,9 @@ function testDrupalSetMessage() {
     $this->assertUniqueText('Non duplicate SafeString / string.');
     $this->assertNoUniqueText('Duplicate SafeString / string.');
 
-    // Render arrays and strings which are equivalent can not be de-duplicated.
+    // Render arrays and strings which are equivalent cannot be de-duplicated.
     // Test this known shortcoming.
+    // @todo Consider resolving this in https://www.drupal.org/node/2545414.
     $this->assertNoUniqueText('Duplicate render array / string');
   }
 
diff --git a/core/modules/system/tests/modules/system_test/src/Controller/SystemTestController.php b/core/modules/system/tests/modules/system_test/src/Controller/SystemTestController.php
index 537887f..ecb25cc 100644
--- a/core/modules/system/tests/modules/system_test/src/Controller/SystemTestController.php
+++ b/core/modules/system/tests/modules/system_test/src/Controller/SystemTestController.php
@@ -142,6 +142,7 @@ public function drupalSetMessageTest() {
 
     // This mixing of types will cause a duplicate even though it is not
     // intended.
+    // @todo Consider resolving this in https://www.drupal.org/node/2545414.
     drupal_set_message(['#markup' => 'Duplicate render array / string']);
     drupal_set_message('Duplicate render array / string');