diff --git a/framework/CHANGELOG.md b/framework/CHANGELOG.md
index 4103f51..6ad8de4 100644
--- a/framework/CHANGELOG.md
+++ b/framework/CHANGELOG.md
@@ -45,10 +45,11 @@ Yii Framework 2 Change Log
 - Bug #3752: `QueryBuilder::batchInsert()` does not typecast input values (qiangxue)
 - Bug #3756: Fix number formatting error for `\yii\base\Formatter` by converting strings to float (kartik-v)
 - Bug #3817: `yii\rbac\PhpManager::getChildren()` returns null instead of expected empty array (qiangxue)
+- Bug #3843: Fixed Menu bug when using `template` with `encodeLabel` => false (creocoder, umneeq)
+- Bug #3863: Fixed incorrect js selector for `\yii\widgets\ActiveForm::errorSummaryCssClass` when it contains multiple classes (creocoder, umneeq)
 - Bug: Fixed inconsistent return of `\yii\console\Application::runAction()` (samdark)
 - Bug: URL encoding for the route parameter added to `\yii\web\UrlManager` (klimov-paul)
 - Bug: Fixed the bug that requesting protected or private action methods would cause 500 error instead of 404 (qiangxue)
-- Bug #3843: Fixed Menu bug when using `template` with `encodeLabel` => false (creocoder, umneeq)
 - Enh #2264: `CookieCollection::has()` will return false for expired or removed cookies (qiangxue)
 - Enh #2435: `yii\db\IntegrityException` is now thrown on database integrity errors instead of general `yii\db\Exception` (samdark)
 - Enh #2837: Error page now shows arguments in stack trace method calls (samdark)
diff --git a/framework/widgets/ActiveForm.php b/framework/widgets/ActiveForm.php
index 66c4d03..d7c91fd 100644
--- a/framework/widgets/ActiveForm.php
+++ b/framework/widgets/ActiveForm.php
@@ -197,7 +197,7 @@ class ActiveForm extends Widget
     protected function getClientOptions()
     {
         $options = [
-            'errorSummary' => '.' . $this->errorSummaryCssClass,
+            'errorSummary' => '.' . implode('.', preg_split('/\s+/', $this->errorSummaryCssClass, -1, PREG_SPLIT_NO_EMPTY)),
             'validateOnSubmit' => $this->validateOnSubmit,
             'errorCssClass' => $this->errorCssClass,
             'successCssClass' => $this->successCssClass,