diff --git a/src/Symfony/Component/Yaml/Inline.php b/src/Symfony/Component/Yaml/Inline.php
index 3a6fe03e8dee6..f42a677dc2d5c 100644
--- a/src/Symfony/Component/Yaml/Inline.php
+++ b/src/Symfony/Component/Yaml/Inline.php
@@ -207,19 +207,7 @@ public static function dump($value, int $flags = 0): string
      */
     public static function isHash($value): bool
     {
-        if ($value instanceof \stdClass || $value instanceof \ArrayObject) {
-            return true;
-        }
-
-        $expectedKey = 0;
-
-        foreach ($value as $key => $val) {
-            if ($key !== $expectedKey++) {
-                return true;
-            }
-        }
-
-        return false;
+        return !\is_array($value) || !array_is_list($value);
     }
 
     /**
diff --git a/src/Symfony/Component/Yaml/composer.json b/src/Symfony/Component/Yaml/composer.json
index e5c6467291794..215d91bd3eae9 100644
--- a/src/Symfony/Component/Yaml/composer.json
+++ b/src/Symfony/Component/Yaml/composer.json
@@ -18,7 +18,8 @@
     "require": {
         "php": ">=7.2.5",
         "symfony/deprecation-contracts": "^2.1",
-        "symfony/polyfill-ctype": "~1.8"
+        "symfony/polyfill-ctype": "^1.8",
+        "symfony/polyfill-php81": "^1.22"
     },
     "require-dev": {
         "symfony/console": "^4.4|^5.0|^6.0"