diff --git a/swh/lister/github/lister.py b/swh/lister/github/lister.py
index 30e686e..40eb4e2 100644
--- a/swh/lister/github/lister.py
+++ b/swh/lister/github/lister.py
@@ -1,73 +1,71 @@
-# Copyright (C) 2017-2019 The Software Heritage developers
+# Copyright (C) 2017-2020 The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
 import re
-import time
 
 from typing import Any
 
 from swh.lister.core.indexing_lister import IndexingHttpLister
 from swh.lister.github.models import GitHubModel
 
 
 class GitHubLister(IndexingHttpLister):
     PATH_TEMPLATE = '/repositories?since=%d'
     MODEL = GitHubModel
     DEFAULT_URL = 'https://api.github.com'
     API_URL_INDEX_RE = re.compile(r'^.*/repositories\?since=(\d+)')
     LISTER_NAME = 'github'
     instance = 'github'  # There is only 1 instance of such lister
     default_min_bound = 0  # type: Any
 
     def get_model_from_repo(self, repo):
         return {
             'uid': repo['id'],
             'indexable': repo['id'],
             'name': repo['name'],
             'full_name': repo['full_name'],
             'html_url': repo['html_url'],
             'origin_url': repo['html_url'],
             'origin_type': 'git',
             'fork': repo['fork'],
         }
 
     def transport_quota_check(self, response):
         x_rate_limit_remaining = response.headers.get('X-RateLimit-Remaining')
         if not x_rate_limit_remaining:
             return False, 0
         reqs_remaining = int(x_rate_limit_remaining)
         if response.status_code == 403 and reqs_remaining == 0:
-            reset_at = int(response.headers['X-RateLimit-Reset'])
-            delay = min(reset_at - time.time(), 3600)
+            delay = int(response.headers['Retry-After'])
             return True, delay
         return False, 0
 
     def get_next_target_from_response(self, response):
         if 'next' in response.links:
             next_url = response.links['next']['url']
             return int(self.API_URL_INDEX_RE.match(next_url).group(1))
 
     def transport_response_simplified(self, response):
         repos = response.json()
         return [self.get_model_from_repo(repo) for repo in repos]
 
     def request_headers(self):
         """(Override) Set requests headers to send when querying the GitHub API
 
         """
         headers = super().request_headers()
         headers['Accept'] = 'application/vnd.github.v3+json'
         return headers
 
     def disable_deleted_repo_tasks(self, index, next_index, keep_these):
         """ (Overrides) Fix provided index value to avoid erroneously disabling
         some scheduler tasks
         """
         # Next listed repository ids are strictly greater than the 'since'
         # parameter, so increment the index to avoid disabling the latest
         # created task when processing a new repositories page returned by
         # the Github API
         return super().disable_deleted_repo_tasks(index + 1, next_index,
                                                   keep_these)
diff --git a/swh/lister/github/tests/test_lister.py b/swh/lister/github/tests/test_lister.py
index f2c085f..c0b2711 100644
--- a/swh/lister/github/tests/test_lister.py
+++ b/swh/lister/github/tests/test_lister.py
@@ -1,81 +1,78 @@
-# Copyright (C) 2017-2019 The Software Heritage developers
+# Copyright (C) 2017-2020 The Software Heritage developers
 # See the AUTHORS file at the top-level directory of this distribution
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
 import re
 import unittest
 
 import requests_mock
 
-from datetime import datetime, timedelta
-
 from swh.lister.core.tests.test_lister import HttpListerTester
 from swh.lister.github.lister import GitHubLister
 
 
 class GitHubListerTester(HttpListerTester, unittest.TestCase):
     Lister = GitHubLister
     test_re = re.compile(r'/repositories\?since=([^?&]+)')
     lister_subdir = 'github'
     good_api_response_file = 'data/https_api.github.com/first_response.json'
     bad_api_response_file = 'data/https_api.github.com/empty_response.json'
     first_index = 0
     last_index = 369
     entries_per_page = 100
     convert_type = int
 
     def response_headers(self, request):
         headers = {'X-RateLimit-Remaining': '1'}
         if self.request_index(request) == self.first_index:
             headers.update({
                 'Link': '<https://api.github.com/repositories?since=%s>;'
                         ' rel="next",'
                         '<https://api.github.com/repositories{?since}>;'
                         ' rel="first"' % self.last_index
             })
         else:
             headers.update({
                 'Link': '<https://api.github.com/repositories{?since}>;'
                         ' rel="first"'
             })
         return headers
 
     def mock_rate_quota(self, n, request, context):
         self.rate_limit += 1
         context.status_code = 403
         context.headers['X-RateLimit-Remaining'] = '0'
-        one_second = int((datetime.now() + timedelta(seconds=1.5)).timestamp())
-        context.headers['X-RateLimit-Reset'] = str(one_second)
+        context.headers['Retry-After'] = '1'   # 1 second
         return '{"error":"dummy"}'
 
     @requests_mock.Mocker()
     def test_scheduled_tasks(self, http_mocker):
         self.scheduled_tasks_test(
             'data/https_api.github.com/next_response.json', 876, http_mocker)
 
 
 def test_lister_github(swh_listers, requests_mock_datadir):
     """Simple github listing should create scheduled tasks
 
     """
     lister = swh_listers['github']
 
     lister.run()
 
     r = lister.scheduler.search_tasks(task_type='load-git')
     assert len(r) == 100
 
     for row in r:
         assert row['type'] == 'load-git'
         # arguments check
         args = row['arguments']['args']
         assert len(args) == 0
 
         # kwargs
         kwargs = row['arguments']['kwargs']
         url = kwargs['url']
         assert url.startswith('https://github.com')
 
         assert row['policy'] == 'recurring'
         assert row['priority'] is None