diff --git a/docker/api/build.py b/docker/api/build.py
index cbef4a8b..5d4e7720 100644
--- a/docker/api/build.py
+++ b/docker/api/build.py
@@ -274,7 +274,10 @@ class BuildApiMixin(object):
                         self._auth_configs, registry
                     )
             else:
-                auth_data = self._auth_configs
+                auth_data = self._auth_configs.copy()
+                # See https://github.com/docker/docker-py/issues/1683
+                if auth.INDEX_NAME in auth_data:
+                    auth_data[auth.INDEX_URL] = auth_data[auth.INDEX_NAME]
 
             log.debug(
                 'Sending auth config ({0})'.format(
diff --git a/docker/auth.py b/docker/auth.py
index ec9c45b9..c3fb062e 100644
--- a/docker/auth.py
+++ b/docker/auth.py
@@ -10,7 +10,7 @@ from . import errors
 from .constants import IS_WINDOWS_PLATFORM
 
 INDEX_NAME = 'docker.io'
-INDEX_URL = 'https://{0}/v1/'.format(INDEX_NAME)
+INDEX_URL = 'https://index.{0}/v1/'.format(INDEX_NAME)
 DOCKER_CONFIG_FILENAME = os.path.join('.docker', 'config.json')
 LEGACY_DOCKER_CONFIG_FILENAME = '.dockercfg'
 TOKEN_USERNAME = '<token>'
@@ -118,7 +118,7 @@ def _resolve_authconfig_credstore(authconfig, registry, credstore_name):
     if not registry or registry == INDEX_NAME:
         # The ecosystem is a little schizophrenic with index.docker.io VS
         # docker.io - in that case, it seems the full URL is necessary.
-        registry = 'https://index.docker.io/v1/'
+        registry = INDEX_URL
     log.debug("Looking for auth entry for {0}".format(repr(registry)))
     store = dockerpycreds.Store(credstore_name)
     try: