diff -u b/core/lib/Drupal/Core/Render/Element/StatusMessages.php b/core/lib/Drupal/Core/Render/Element/StatusMessages.php
--- b/core/lib/Drupal/Core/Render/Element/StatusMessages.php
+++ b/core/lib/Drupal/Core/Render/Element/StatusMessages.php
@@ -73,7 +73,6 @@
    * @see drupal_get_messages()
    */
   public static function renderMessages($type) {
-    $render = [];
     $messages = drupal_get_messages($type);
     // Render the messages.
     $render = [
reverted:
--- b/core/misc/announce.js
+++ a/core/misc/announce.js
@@ -50,23 +50,21 @@
   /**
    * Concatenates announcements to a single string; appends to the live region.
    */
+  function announce() {
-  function processAnnounce() {
     var text = [];
     var priority = 'polite';
     var announcement;
 
+    // Create an array of announcement strings to be joined and appended to the
+    // aria live region.
+    var il = announcements.length;
+    for (var i = 0; i < il; i++) {
+      announcement = announcements.pop();
+      text.unshift(announcement.text);
+      // If any of the announcements has a priority of assertive then the group
+      // of joined announcements will have this priority.
+      if (announcement.priority === 'assertive') {
+        priority = 'assertive';
-    if (announcements.length) {
-      // Create an array of announcement strings to be joined and appended to
-      // the aria live region.
-      var il = announcements.length;
-      for (var i = 0; i < il; i++) {
-        announcement = announcements.pop();
-        text.unshift(announcement.text);
-        // If any of the announcements has a priority of assertive then the
-        // group of joined announcements will have this priority.
-        if (announcement.priority === 'assertive') {
-          priority = 'assertive';
-        }
       }
     }
 
@@ -83,13 +81,8 @@
       // The live text area is updated. Allow the AT to announce the text.
       liveElement.setAttribute('aria-busy', 'false');
     }
-
   }
 
-  // 200 ms is right at the cusp where humans notice a pause, so we will wait
-  // at most this much time before the set of queued announcements is read.
-  var debouncedProcessAnnounce = debounce(processAnnounce, 200);
-
   /**
    * Triggers audio UAs to read the supplied text.
    *
@@ -103,24 +96,25 @@
    *
    * @param {string} text
    *   A string to be read by the UA.
+   * @param {string} [priority='polite']
-   * @param {string} priority
    *   A string to indicate the priority of the message. Can be either
    *   'polite' or 'assertive'.
    *
+   * @return {function}
+   *   The return of the call to debounce.
+   *
    * @see http://www.w3.org/WAI/PF/aria-practices/#liveprops
    */
   Drupal.announce = function (text, priority) {
+    // Save the text and priority into a closure variable. Multiple simultaneous
+    // announcements will be concatenated and read in sequence.
+    announcements.push({
+      text: text,
+      priority: priority
+    });
+    // Immediately invoke the function that debounce returns. 200 ms is right at
+    // the cusp where humans notice a pause, so we will wait
+    // at most this much time before the set of queued announcements is read.
+    return (debounce(announce, 200)());
-    if (typeof text === 'string') {
-      // Save the text and priority into a closure variable. Multiple
-      // simultaneous announcements will be concatenated and read in sequence.
-      announcements.push({
-        text: text,
-        priority: priority
-      });
-      debouncedProcessAnnounce(announcements);
-    }
-    else {
-      throw new Error(Drupal.t('"text" passed Drupal.announce must be a string.'));
-    }
   };
 }(Drupal, Drupal.debounce));
diff -u b/core/misc/message.js b/core/misc/message.js
--- b/core/misc/message.js
+++ b/core/misc/message.js
@@ -62,8 +62,9 @@
       options = options || {};
       // Send message to screen reader.
       announce(message, type, options);
-      // Generate a unique key to allow message deletion.
-      options.index = Math.random().toFixed(15).replace('0.', '');
+      // Use the provided index for the message or generate a unique key to
+      // allow message deletion.
+      options.index = options.index || Math.random().toFixed(15).replace('0.', '');
       messageWrapper.innerHTML += Drupal.theme('message', {text: message, type: type}, options);
 
       return options.index;
@@ -74,7 +75,7 @@
      *
      * @name Drupal.message~messageDefinition.remove
      *
-     * @param {string|Array.<string>} messages
+     * @param {string|Array.<string>} index
      *   Index of the message to remove, as returned by
      *   {@link Drupal.message~messageDefinition.add}, or an
      *   array of indexes.
@@ -82,14 +83,14 @@
      * @return {number}
      *  Number of removed messages.
      */
-    function messageRemove(messages) {
+    function messageRemove(index) {
       // If there is no argument or if the argument is an empty array,
       // no message can be removed.
-      if (!messages || (Array.isArray(messages) && messages.length === 0)) {
+      if (!index || (Array.isArray(index) && index.length === 0)) {
         return 0;
       }
 
-      var removeSelectors = (Array.isArray(messages) ? messages : [messages])
+      var removeSelectors = (Array.isArray(index) ? index : [index])
         .map(function (messageIndex) {
           return '[data-drupal-message="' + messageIndex + '"]';
         });
@@ -154,12 +155,15 @@
   function announce(message, type, options) {
     // Check this. Might be too much.
     if (!options.priority && type !== 'status') {
-      options.priority = 'assertive';
+      options.priority = 'polite';
     }
+    // Always announce the priority of the upcomming message.
+    Drupal.announce(options.priority);
+
     // If screen reader message is not disabled announce screen reader specific
     // text or fallback to the displayed message.
     if (options.announce !== '') {
-      Drupal.announce(options.announce || message, options.priority);
+      Drupal.announce(message, options.priority);
     }
   }
 
diff -u b/core/modules/system/tests/modules/js_message_test/src/Controller/JSMessageTestController.php b/core/modules/system/tests/modules/js_message_test/src/Controller/JSMessageTestController.php
--- b/core/modules/system/tests/modules/js_message_test/src/Controller/JSMessageTestController.php
+++ b/core/modules/system/tests/modules/js_message_test/src/Controller/JSMessageTestController.php
@@ -24,7 +24,7 @@
         '#title' => "Message area: $messagesSelector",
         '#attributes' => [
           'data-drupal-messages-area' => $messagesSelector,
-        ]
+        ],
       ];
       foreach (JsMessageTestCases::getTypes() as $type) {
         $buttons[$messagesSelector]["add-$type"] = [
@@ -121,7 +121,7 @@
             'types' => JsMessageTestCases::getTypes(),
           ],
         ],
-      ]
+      ],
     ];
   }