src/Reflection/Adapter/ReflectionObject.php
public function isSubclassOf($class)
    {
        $realParentClassNames = $this->betterReflectionObject->getParentClassNames();

        $parentClassNames = array_combine(array_map(static function (string $parentClassName) : string {
            return strtolower($parentClassName);
        }, $realParentClassNames), $realParentClassNames);

        $realParentClassName = $parentClassNames[strtolower($class)] ?? $class;

        return $this->betterReflectionObject->isSubclassOf($realParentClassName);
    }
public function isSubclassOf($class)
    {
        $realParentClassNames = $this->betterReflectionObject->getParentClassNames();

        $parentClassNames = array_combine(array_map(static function (string $parentClassName) : string {
            return strtolower($parentClassName);
        }, $realParentClassNames), $realParentClassNames);

        $realParentClassName = $parentClassNames[strtolower($class)] ?? $class;

        return $this->betterReflectionObject->isSubclassOf($realParentClassName);
    }
{@inheritDoc}