diff --git a/docker/auth/auth.py b/docker/auth/auth.py
index 56c42ecacd..4af741e072 100644
--- a/docker/auth/auth.py
+++ b/docker/auth/auth.py
@@ -98,12 +98,6 @@ def encode_header(auth):
     return base64.b64encode(auth_json)
 
 
-def encode_full_header(auth):
-    """ Returns the given auth block encoded for the X-Registry-Config header.
-    """
-    return encode_header({'configs': auth})
-
-
 def parse_auth(entries):
     """
     Parses authentication entries
diff --git a/docker/client.py b/docker/client.py
index 9084689594..41dd03aee2 100644
--- a/docker/client.py
+++ b/docker/client.py
@@ -140,9 +140,14 @@ def build(self, path=None, tag=None, quiet=False, fileobj=None,
             if self._auth_configs:
                 if headers is None:
                     headers = {}
-                headers['X-Registry-Config'] = auth.encode_full_header(
-                    self._auth_configs
-                )
+                if utils.compare_version('1.19', self._version) >= 0:
+                    headers['X-Registry-Config'] = auth.encode_header(
+                        self._auth_configs
+                    )
+                else:
+                    headers['X-Registry-Config'] = auth.encode_header({
+                        'configs': self._auth_configs
+                    })
 
         response = self._post(
             u,