diff --git a/EventListener/AutoAddMissingTranslations.php b/EventListener/AutoAddMissingTranslations.php
index 5cfcac66..844888e5 100644
--- a/EventListener/AutoAddMissingTranslations.php
+++ b/EventListener/AutoAddMissingTranslations.php
@@ -11,7 +11,6 @@
 
 namespace Translation\Bundle\EventListener;
 
-use Symfony\Component\HttpKernel\Event\PostResponseEvent;
 use Symfony\Component\HttpKernel\Event\TerminateEvent;
 use Symfony\Component\Translation\DataCollectorTranslator;
 use Translation\Bundle\Service\StorageService;
@@ -32,9 +31,6 @@ final class AutoAddMissingTranslations
      */
     private $storage;
 
-    /**
-     * @param DataCollectorTranslator $translator
-     */
     public function __construct(StorageService $storage, DataCollectorTranslator $translator = null)
     {
         $this->dataCollector = $translator;
@@ -56,10 +52,3 @@ public function onTerminate(TerminateEvent $event): void
         }
     }
 }
-
-// PostResponseEvent have been renamed into ResponseEvent in sf 4.3
-// @see https://github.com/symfony/symfony/blob/master/UPGRADE-4.3.md#httpkernel
-// To be removed once sf ^4.3 become the minimum supported version.
-if (!class_exists(TerminateEvent::class) && class_exists(PostResponseEvent::class)) {
-    class_alias(PostResponseEvent::class, TerminateEvent::class);
-}
diff --git a/EventListener/EditInPlaceResponseListener.php b/EventListener/EditInPlaceResponseListener.php
index 9c296e08..37a6ea52 100644
--- a/EventListener/EditInPlaceResponseListener.php
+++ b/EventListener/EditInPlaceResponseListener.php
@@ -12,7 +12,6 @@
 namespace Translation\Bundle\EventListener;
 
 use Symfony\Component\Asset\Packages;
-use Symfony\Component\HttpKernel\Event\FilterResponseEvent;
 use Symfony\Component\HttpKernel\Event\ResponseEvent;
 use Symfony\Component\Routing\Generator\UrlGeneratorInterface;
 use Translation\Bundle\EditInPlace\ActivatorInterface;
@@ -128,10 +127,3 @@ public function onKernelResponse(ResponseEvent $event): void
         $event->getResponse()->setContent($content);
     }
 }
-
-// FilterResponseEvent have been renamed into ResponseEvent in sf 4.3
-// @see https://github.com/symfony/symfony/blob/master/UPGRADE-4.3.md#httpkernel
-// To be removed once sf ^4.3 become the minimum supported version.
-if (!class_exists(ResponseEvent::class) && class_exists(FilterResponseEvent::class)) {
-    class_alias(FilterResponseEvent::class, ResponseEvent::class);
-}
diff --git a/Resources/public/js/editInPlace.js b/Resources/public/js/editInPlace.js
index aa412d9f..cf9b52e0 100644
--- a/Resources/public/js/editInPlace.js
+++ b/Resources/public/js/editInPlace.js
@@ -8,7 +8,10 @@
  */
 (function () {
     if (typeof customElements.define !== "undefined") {
-        customElements.define("x-trans", HTMLElement);
+        // it is not possible to use HTMLElement directly
+        class XTrans extends HTMLElement {}
+
+        customElements.define("x-trans", XTrans);
 
         return;
     }