diff --git a/swh/lister/github/lister.py b/swh/lister/github/lister.py
--- a/swh/lister/github/lister.py
+++ b/swh/lister/github/lister.py
@@ -1,10 +1,9 @@
-# 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
 
@@ -39,8 +38,7 @@
             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
 
diff --git a/swh/lister/github/tests/test_lister.py b/swh/lister/github/tests/test_lister.py
--- a/swh/lister/github/tests/test_lister.py
+++ b/swh/lister/github/tests/test_lister.py
@@ -1,4 +1,4 @@
-# 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
@@ -8,8 +8,6 @@
 
 import requests_mock
 
-from datetime import datetime, timedelta
-
 from swh.lister.core.tests.test_lister import HttpListerTester
 from swh.lister.github.lister import GitHubLister
 
@@ -45,8 +43,7 @@
         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()