diff --git a/core/lib/Drupal/Component/Utility/EscapedString.php b/core/lib/Drupal/Component/Utility/EscapedString.php
index 46c819a..9a3dcd8 100644
--- a/core/lib/Drupal/Component/Utility/EscapedString.php
+++ b/core/lib/Drupal/Component/Utility/EscapedString.php
@@ -12,7 +12,7 @@
  *
  * @ingroup sanitization
  */
-class EscapedString implements SafeStringInterface, \Countable {
+class EscapedString implements EscapedStringInterface {
 
   /**
    * The string to escape.
diff --git a/core/lib/Drupal/Component/Utility/EscapedStringInterface.php b/core/lib/Drupal/Component/Utility/EscapedStringInterface.php
new file mode 100644
index 0000000..68bcdad
--- /dev/null
+++ b/core/lib/Drupal/Component/Utility/EscapedStringInterface.php
@@ -0,0 +1,27 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Component\Utility\EscapedStringInterface.
+ */
+
+namespace Drupal\Component\Utility;
+
+/**
+ * Marks an object's __toString() method as returning escaped HTML.
+ *
+ * This interface should only be used on objects that emit escaped strings from
+ * their __toString() method. If the output of __toString() contains unescaped
+ * HTML, it must not be used.
+ *
+ * @ingroup sanitization
+ *
+ */
+interface EscapedStringInterface extends SafeStringInterface, \Countable {
+
+  /**
+   * Returns an escaped string..
+   */
+  public function __toString();
+
+}
diff --git a/core/lib/Drupal/Component/Utility/SafeMarkup.php b/core/lib/Drupal/Component/Utility/SafeMarkup.php
index e1ee718..2e3b115 100644
--- a/core/lib/Drupal/Component/Utility/SafeMarkup.php
+++ b/core/lib/Drupal/Component/Utility/SafeMarkup.php
@@ -25,6 +25,8 @@
  * @link theme_render theme and render systems @endlink so that the output can
  * can be themed, escaped, and altered properly.
  *
+ * @deprecated Will be removed before Drupal 9.0.0.
+ *
  * @see TwigExtension::escapeFilter()
  * @see twig_render_template()
  * @see sanitization
@@ -62,8 +64,8 @@ public static function isSafe($string, $strategy = 'html') {
    * @param string $text
    *   The text to be checked or processed.
    *
-   * @return \Drupal\Component\Utility\EscapedString
-   *   A SafeStringInterface object that escapes when rendered to string.
+   * @return \Drupal\Component\Utility\EscapedStringInterface
+   *   An EscapedString object that escapes when rendered to string.
    *
    * @ingroup sanitization
    *