diff -u b/core/modules/filter/src/Element/ProcessedText.php b/core/modules/filter/src/Element/ProcessedText.php
--- b/core/modules/filter/src/Element/ProcessedText.php
+++ b/core/modules/filter/src/Element/ProcessedText.php
@@ -124,7 +124,7 @@
     // safe, but it has been passed through the filter system and checked with
     // a text format, so it must be printed as is. (See the note about security
     // in the method documentation above.)
-    $element['#markup'] = FilteredString($text);
+    $element['#markup'] = FilteredString::create($text);
 
     // Set the updated bubbleable rendering metadata and the text format's
     // cache tag.