Undefined array key 0 on contentful/contentful-management/src/Exception/RateLimitExceededException.php line 51

Sometimes i get an exception : Undefined array key 0
raised on contentful/contentful-management/src/Exception/RateLimitExceededException.php at line 51
=> in contructor : 
        $this->hourLimit = (int) $response->getHeader('X-Contentful-RateLimit-Hour-Limit')[0];

Maybe header is not well generated?