diff --git a/src/Symfony/Component/HttpClient/HttpClientTrait.php b/src/Symfony/Component/HttpClient/HttpClientTrait.php
index de1689490e62..57d48aade8db 100644
--- a/src/Symfony/Component/HttpClient/HttpClientTrait.php
+++ b/src/Symfony/Component/HttpClient/HttpClientTrait.php
@@ -189,7 +189,7 @@ private static function mergeDefaultOptions(array $options, array $defaultOption
 
         $options += $defaultOptions;
 
-        foreach (self::$emptyDefaults ?? [] as $k => $v) {
+        foreach (isset(self::$emptyDefaults) ? self::$emptyDefaults : [] as $k => $v) {
             if (!isset($options[$k])) {
                 $options[$k] = $v;
             }