Tiered policy and unexpected behavior of api key

There is no quota set. I only have 6 request per 3600s. it only allows 3 of them and the next ones respond with ‘429’ ‘too many requests’.
The response headers for the calls with 200 status is like this
< X-Ratelimit-Limit: -1
< X-Ratelimit-Remaining: -1
< X-Ratelimit-Reset: 1507744130

for the responses with 429 status, I don’t receive such header