diff --git a/core/misc/ajax.es6.js b/core/misc/ajax.es6.js
index 950e9c582c..e0f6355113 100644
--- a/core/misc/ajax.es6.js
+++ b/core/misc/ajax.es6.js
@@ -1620,6 +1620,8 @@
 
     add_js(ajax, response) {
       const deferred = $.Deferred();
+      const parentEl = document.querySelector(response.selector || 'body');
+      const settings = ajax.settings || drupalSettings;
       const scriptsSrc = response.data.map((script) => {
         // loadjs requires a unique ID, AJAX instances' `instanceIndex` are
         // guaranteed to be unique.
@@ -1628,16 +1630,11 @@
         loadjs(script.src, uniqueBundleID, {
           async: !!script.async,
           before(path, scriptEl) {
-            let selector = 'body';
-            if (response.selector) {
-              selector = response.selector;
-            }
             if (script.defer) {
               scriptEl.defer = true;
             }
             // To avoid synchronous XMLHttpRequest on the main thread and break
             // load dependency, it should not use jQuery.
-            const parentEl = document.querySelector(selector);
             if (response.method === 'insertBefore') {
               parentEl.insertBefore(scriptEl, parentEl.firstChild);
             }
@@ -1652,6 +1649,7 @@
       });
       loadjs.ready(scriptsSrc, {
         success() {
+          Drupal.attachBehaviors(parentEl, settings);
           deferred.resolve();
         },
       });
diff --git a/core/misc/ajax.js b/core/misc/ajax.js
index 1700824e1f..37da5c271d 100644
--- a/core/misc/ajax.js
+++ b/core/misc/ajax.js
@@ -679,20 +679,17 @@ function _toConsumableArray(arr) { if (Array.isArray(arr)) { for (var i = 0, arr
     },
     add_js: function add_js(ajax, response) {
       var deferred = $.Deferred();
+      var parentEl = document.querySelector(response.selector || 'body');
+      var settings = ajax.settings || drupalSettings;
       var scriptsSrc = response.data.map(function (script) {
         var uniqueBundleID = script.src + ajax.instanceIndex;
         loadjs(script.src, uniqueBundleID, {
           async: !!script.async,
           before: function before(path, scriptEl) {
-            var selector = 'body';
-            if (response.selector) {
-              selector = response.selector;
-            }
             if (script.defer) {
               scriptEl.defer = true;
             }
 
-            var parentEl = document.querySelector(selector);
             if (response.method === 'insertBefore') {
               parentEl.insertBefore(scriptEl, parentEl.firstChild);
             } else {
@@ -706,6 +703,7 @@ function _toConsumableArray(arr) { if (Array.isArray(arr)) { for (var i = 0, arr
       });
       loadjs.ready(scriptsSrc, {
         success: function success() {
+          Drupal.attachBehaviors(parentEl, settings);
           deferred.resolve();
         }
       });