diff --git a/tests/test_auth.py b/tests/test_auth.py
index a33211c2..cb53ba82 100644
--- a/tests/test_auth.py
+++ b/tests/test_auth.py
@@ -19,7 +19,7 @@ class TestAuth:
         requests.__version__ == '0.13.6',
         reason='Redirects with prefetch=False are broken in Requests 0.13.6')
     def test_digest_auth(self, httpbin, argument_name):
-        r = http('{}=digest'.format(argument_name), '--auth=user:password',
+        r = http(argument_name + '=digest', '--auth=user:password',
                  'GET', httpbin.url + '/digest-auth/auth/user/password')
         assert HTTP_OK in r
         assert r.json == {'authenticated': True, 'user': 'user'}