diff --git a/swh/lister/gitlab/lister.py b/swh/lister/gitlab/lister.py
index d24d773..e502630 100644
--- a/swh/lister/gitlab/lister.py
+++ b/swh/lister/gitlab/lister.py
@@ -1,122 +1,120 @@
 # Copyright (C) 2018 the Software Heritage developers
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
 import random
 import time
 
 from ..core.page_by_page_lister import PageByPageHttpLister
 from .models import GitLabModel
 
 
 class GitLabLister(PageByPageHttpLister):
     # Template path expecting an integer that represents the page id
     PATH_TEMPLATE = '/projects?page=%d&order_by=id'
     MODEL = GitLabModel
     LISTER_NAME = 'gitlab'
 
     def __init__(self, api_baseurl=None, instance=None,
                  override_config=None, sort='asc', per_page=20):
         super().__init__(api_baseurl=api_baseurl,
                          override_config=override_config)
         self.instance = instance
         self.PATH_TEMPLATE = '%s&sort=%s' % (self.PATH_TEMPLATE, sort)
         if per_page != 20:
             self.PATH_TEMPLATE = '%s&per_page=%s' % (
                 self.PATH_TEMPLATE, per_page)
 
     @property
     def ADDITIONAL_CONFIG(self):
         """Override additional config as the 'credentials' structure change
            between the ancestor classes and this class.
 
            cf. request_params method below
 
         """
         default_config = super().ADDITIONAL_CONFIG
         # 'credentials' is a dict of (instance, {username, password}) dict
         default_config['credentials'] = ('dict', {})
         return default_config
 
     def request_params(self, identifier):
         """Get the full parameters passed to requests given the
         transport_request identifier.
 
         For the gitlab lister, the 'credentials' entries is configured
         per instance. For example:
 
         - credentials:
           - gitlab.com:
             - username: user0
               password: <pass>
             - username: user1
               password: <pass>
             - ...
           - other-gitlab-instance:
             ...
 
         """
         params = {
             'headers': self.request_headers() or {}
         }
-        # Retrieve the credentials per instance
-        creds = self.config['credentials']
-        if creds:
-            creds_lister = creds[self.instance]
-            auth = random.choice(creds_lister) if creds else None
+        creds_lister = self.config['credentials'].get(self.instance)
+        if creds_lister:
+            auth = random.choice(creds_lister)
             if auth:
                 params['auth'] = (auth['username'], auth['password'])
         return params
 
     def uid(self, repo):
         return '%s/%s' % (self.instance, repo['path_with_namespace'])
 
     def get_model_from_repo(self, repo):
         return {
             'instance': self.instance,
             'uid': self.uid(repo),
             'name': repo['name'],
             'full_name': repo['path_with_namespace'],
             'html_url': repo['web_url'],
             'origin_url': repo['http_url_to_repo'],
             'origin_type': 'git',
             'description': repo['description'],
         }
 
     def transport_quota_check(self, response):
         """Deal with rate limit if any.
 
         """
         # not all gitlab instance have rate limit
         if 'RateLimit-Remaining' in response.headers:
             reqs_remaining = int(response.headers['RateLimit-Remaining'])
             if response.status_code == 403 and reqs_remaining == 0:
                 reset_at = int(response.headers['RateLimit-Reset'])
                 delay = min(reset_at - time.time(), 3600)
                 return True, delay
         return False, 0
 
     def _get_int(self, headers, key):
         _val = headers.get(key)
         if _val:
             return int(_val)
 
     def get_next_target_from_response(self, response):
         """Determine the next page identifier.
 
         """
         return self._get_int(response.headers, 'x-next-page')
 
     def get_pages_information(self):
         """Determine pages information.
 
         """
         response = self.transport_head(identifier=1)
         h = response.headers
         return (self._get_int(h, 'x-total'),
                 self._get_int(h, 'x-total-pages'),
                 self._get_int(h, 'x-per-page'))
 
     def transport_response_simplified(self, response):
         repos = response.json()
         return [self.get_model_from_repo(repo) for repo in repos]