diff --git a/docker/auth/__init__.py b/docker/auth/__init__.py
index 66acdb36..d068b7fa 100644
--- a/docker/auth/__init__.py
+++ b/docker/auth/__init__.py
@@ -3,5 +3,5 @@ from .auth import (
     encode_header,
     load_config,
     resolve_authconfig,
-    resolve_repository_name
+    resolve_repository_name,
 )  # flake8: noqa
\ No newline at end of file
diff --git a/docker/auth/auth.py b/docker/auth/auth.py
index fe53c766..86939103 100644
--- a/docker/auth/auth.py
+++ b/docker/auth/auth.py
@@ -75,7 +75,7 @@ def resolve_authconfig(authconfig, registry=None):
     # Default to the public index server
     registry = registry or INDEX_URL
 
-    # Ff its not the index server there are three cases:
+    # If it's not the index server there are three cases:
     #
     # 1. this is a full config url -> it should be used as is
     # 2. it could be a full url, but with the wrong protocol
@@ -84,7 +84,7 @@ def resolve_authconfig(authconfig, registry=None):
     # as there is only one auth entry which is fully qualified we need to start
     # parsing and matching
     if '/v1/' not in registry:
-        registry = registry + '/v1/'
+        registry = os.path.join(registry, 'v1/')
     if not registry.startswith('http:') and not registry.startswith('https:'):
         registry = 'https://' + registry
 
diff --git a/tests/utils_test.py b/tests/utils_test.py
index 2708302e..9b6461f4 100644
--- a/tests/utils_test.py
+++ b/tests/utils_test.py
@@ -8,6 +8,7 @@ from docker.utils import (
     parse_repository_tag, parse_host, convert_filters, kwargs_from_env,
     create_host_config
 )
+from docker.auth import resolve_authconfig
 
 
 class UtilsTest(unittest.TestCase):
@@ -100,6 +101,60 @@ class UtilsTest(unittest.TestCase):
         empty_config = create_host_config()
         self.assertEqual(empty_config, {})
 
+    def test_resolve_authconfig(self):
+        auth_config = {
+            'https://index.docker.io/v1/': {'auth': 'indexuser'},
+            'http://my.registry.net/v1/': {'auth': 'privateuser'}
+        }
+        # hostname only
+        self.assertEqual(
+            resolve_authconfig(auth_config, 'my.registry.net'),
+            {'auth': 'privateuser'}
+        )
+        # no protocol
+        self.assertEqual(
+            resolve_authconfig(auth_config, 'my.registry.net/v1/'),
+            {'auth': 'privateuser'}
+        )
+        # no path
+        self.assertEqual(
+            resolve_authconfig(auth_config, 'http://my.registry.net'),
+            {'auth': 'privateuser'}
+        )
+        # no path, trailing slash
+        self.assertEqual(
+            resolve_authconfig(auth_config, 'http://my.registry.net/'),
+            {'auth': 'privateuser'}
+        )
+        # no path, wrong secure protocol
+        self.assertEqual(
+            resolve_authconfig(auth_config, 'https://my.registry.net'),
+            {'auth': 'privateuser'}
+        )
+        # no path, wrong insecure protocol
+        self.assertEqual(
+            resolve_authconfig(auth_config, 'http://index.docker.io'),
+            {'auth': 'indexuser'}
+        )
+        # with path, wrong protocol
+        self.assertEqual(
+            resolve_authconfig(auth_config, 'https://my.registry.net/v1/'),
+            {'auth': 'privateuser'}
+        )
+        # default registry
+        self.assertEqual(
+            resolve_authconfig(auth_config), {'auth': 'indexuser'}
+        )
+        # default registry (explicit None)
+        self.assertEqual(
+            resolve_authconfig(auth_config, None), {'auth': 'indexuser'}
+        )
+        # fully explicit
+        self.assertEqual(
+            resolve_authconfig(auth_config, 'http://my.registry.net/v1/'),
+            {'auth': 'privateuser'}
+        )
+
 
 if __name__ == '__main__':
     unittest.main()