diff --git a/core/includes/bootstrap.inc b/core/includes/bootstrap.inc
index d0ab3ae..4be3e9e 100644
--- a/core/includes/bootstrap.inc
+++ b/core/includes/bootstrap.inc
@@ -562,8 +562,8 @@ function drupal_set_message($message = NULL, $type = 'status', $repeat = FALSE)
     }
 
     $new = array(
-      'safe' => SafeMarkup::isSafe($message),
-      'message' => (string) $message,
+      'safe' => (!is_array($message) && SafeMarkup::isSafe($message)),
+      'message' => $message,
     );
     if ($repeat || !in_array($new, $_SESSION['messages'][$type])) {
       $_SESSION['messages'][$type][] = $new;
@@ -610,7 +610,7 @@ function drupal_get_messages($type = NULL, $clear_queue = TRUE) {
         // the messages also needs to be stored in the session. We retrieve the
         // safe status here and determine whether to mark the string as safe or
         // let autoescape do its thing. See drupal_set_message().
-        if ($message['safe']) {
+        if ($message['safe']) { // Only set when the message is not an array.
           $message['message'] = SafeMarkup::set($message['message']);
         }
         $messages[$message_type][$key] = $message['message'];
diff --git a/core/modules/system/src/Tests/Bootstrap/DrupalSetMessageTest.php b/core/modules/system/src/Tests/Bootstrap/DrupalSetMessageTest.php
index bf130b5..79c824e 100644
--- a/core/modules/system/src/Tests/Bootstrap/DrupalSetMessageTest.php
+++ b/core/modules/system/src/Tests/Bootstrap/DrupalSetMessageTest.php
@@ -31,7 +31,7 @@ function testSetRemoveMessages() {
     // removes the first before it is displayed.
     $this->drupalGet('system-test/drupal-set-message');
     $this->assertNoText('First message (removed).');
-    $this->assertText('Second message (not removed).');
+    $this->assertRaw(t('Second message with <em>markup!</em> (not removed).'));
   }
 
   /**
@@ -48,7 +48,7 @@ function testDuplicatedMessages() {
    */
   function testRenderArrayMessages() {
     $this->drupalGet('system-test/drupal-set-message');
-    $this->assertText('Render array');
+    $this->assertRaw('Render array with <em>markup!</em>');
   }
 
 }
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 3b69300..3e5fe18 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
@@ -101,10 +101,10 @@ public function mainContentFallback() {
   public function drupalSetMessageTest() {
     // Set two messages.
     drupal_set_message('First message (removed).');
-    drupal_set_message('Second message (not removed).');
+    drupal_set_message(t('Second message with <em>markup!</em> (not removed).'));
 
     // Add a render array message.
-    drupal_set_message(['#markup' => 'Render array']);
+    drupal_set_message(['#markup' => 'Render array with <em>markup!</em>']);
 
     // Remove the first.
     unset($_SESSION['messages']['status'][0]);