diff -u b/core/misc/ajax.es6.js b/core/misc/ajax.es6.js
--- b/core/misc/ajax.es6.js
+++ b/core/misc/ajax.es6.js
@@ -1062,13 +1062,13 @@
       // When there are other types of top-level nodes, the response needs to be
       // wrapped.
       else {
-        const hasCommentNodes = responseDataNodes.some(
-          element => element.nodeType === Node.COMMENT_NODE,
+        const onlyTextOrCommentNodes = responseDataNodes.every(
+          element => element.nodeType === Node.COMMENT_NODE || element.nodeType === Node.TEXT_NODE,
         );
-        // If response.data contains only one TEXT_ELEMENT, TEXT_ELEMENT and
+        // If response.data contains only nodes of the type TEXT_NODE or
         // COMMENT_NODE, or the wrapping element is not styled as a block,
         // response.data will be wrapped with SPAN.
-        if (responseDataNodes.length === 1 || hasCommentNodes || $wrapper.css('display') !== 'block') {
+        if (onlyTextOrCommentNodes || $wrapper.css('display') !== 'block') {
           $newContent = $('<span></span>');
         }
         else {
diff -u b/core/misc/ajax.js b/core/misc/ajax.js
--- b/core/misc/ajax.js
+++ b/core/misc/ajax.js
@@ -500,11 +500,11 @@
       if (onlyElementNodes) {
         $newContent = $(trimmedData);
       } else {
-          var hasCommentNodes = responseDataNodes.some(function (element) {
-            return element.nodeType === Node.COMMENT_NODE;
+          var onlyTextOrCommentNodes = responseDataNodes.every(function (element) {
+            return element.nodeType === Node.COMMENT_NODE || element.nodeType === Node.TEXT_NODE;
           });
 
-          if (responseDataNodes.length === 1 || hasCommentNodes || $wrapper.css('display') !== 'block') {
+          if (onlyTextOrCommentNodes || $wrapper.css('display') !== 'block') {
             $newContent = $('<span></span>');
           } else {
             $newContent = $('<div></div>');
diff -u b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxTest.php b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxTest.php
--- b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxTest.php
+++ b/core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxTest.php
@@ -149,7 +149,7 @@
       [
         'method' => 'html',
         'render_type' => 'mixed',
-        'expected' => '<span class="processed"> foo <!-- COMMENT -->  foo bar<div class="a class"><p>some string</p></div> additional not wrapped strings, <!-- ANOTHER COMMENT --> <p>final string</p></span>',
+        'expected' => '<div class="processed"> foo <!-- COMMENT -->  foo bar<div class="a class"><p>some string</p></div> additional not wrapped strings, <!-- ANOTHER COMMENT --> <p>final string</p></div>',
       ],
       // Test that when the response has only top-level node elements, they
       // are processed properly without extra wrapping.