diff --git a/src/Symfony/Component/Translation/Loader/XliffFileLoader.php b/src/Symfony/Component/Translation/Loader/XliffFileLoader.php
index a949e59ce4..35e2d9c10c 100644
--- a/src/Symfony/Component/Translation/Loader/XliffFileLoader.php
+++ b/src/Symfony/Component/Translation/Loader/XliffFileLoader.php
@@ -76,7 +76,7 @@ class XliffFileLoader implements LoaderInterface
     private function extractXliff1(\DOMDocument $dom, MessageCatalogue $catalogue, string $domain)
     {
         $xml = simplexml_import_dom($dom);
-        $encoding = strtoupper($dom->encoding);
+        $encoding = $dom->encoding ? strtoupper($dom->encoding) : null;
 
         $namespace = 'urn:oasis:names:tc:xliff:document:1.2';
         $xml->registerXPathNamespace('xliff', $namespace);