diff --git a/src/Resolver/EnumOrScalar.php b/src/Resolver/EnumOrScalar.php
index fad2170..043e8d5 100644
--- a/src/Resolver/EnumOrScalar.php
+++ b/src/Resolver/EnumOrScalar.php
@@ -29,7 +29,7 @@ public function resolve(string $propertyName, array $propertyTypes, array $data)
             );
         }
 
-        $value = $data[$propertyName] ?? array_shift($data);
+        $value = array_key_exists($propertyName, $data) ? $data[$propertyName] : array_shift($data);
         if ((is_string($value) || is_int($value)) && $enumClass::tryFrom($value) !== null) {
             return $enum;
         }