Extending the Filesystem class in Laravel 5

I'm having some problems with the Filesystem class. To solve my problem, I want to change the put () function of this:

public function put($path, $contents, $lock = false)
{
    return file_put_contents($path, $contents, $lock ? LOCK_EX : 0);
}

for this:

public function put($path, $contents, $lock = false)
{
    return file_put_contents($path, $contents);
}

What is the best way to do this?