diff --git a/tempest/lib/api_schema/response/compute/v2_1/servers.py b/tempest/lib/api_schema/response/compute/v2_1/servers.py
index 485c51a..3289f04 100644
--- a/tempest/lib/api_schema/response/compute/v2_1/servers.py
+++ b/tempest/lib/api_schema/response/compute/v2_1/servers.py
@@ -267,12 +267,13 @@
     'type': 'object',
     'properties': {
         'id': {'type': 'string'},
-        'device': {'type': 'string'},
+        'device': {'type': ['string', 'null']},
         'volumeId': {'type': 'string'},
         'serverId': {'type': ['integer', 'string']}
     },
     'additionalProperties': False,
-    'required': ['id', 'device', 'volumeId', 'serverId']
+    # 'device' is optional in response.
+    'required': ['id', 'volumeId', 'serverId']
 }
 
 attach_volume = {
diff --git a/tempest/lib/auth.py b/tempest/lib/auth.py
index e269fd1..2d20a0b 100644
--- a/tempest/lib/auth.py
+++ b/tempest/lib/auth.py
@@ -325,13 +325,24 @@
 
         parts = urlparse.urlparse(_base_url)
         if filters.get('api_version', None) is not None:
+            version_path = '/%s' % filters['api_version']
             path = re.sub(r'(^|/)+v\d+(?:\.\d+)?',
-                          '/' + filters['api_version'],
+                          version_path,
                           parts.path,
                           count=1)
-            _base_url = _base_url.replace(parts.path, path)
+            _base_url = urlparse.urlunparse((parts.scheme,
+                                             parts.netloc,
+                                             path or version_path,
+                                             parts.params,
+                                             parts.query,
+                                             parts.fragment))
         if filters.get('skip_path', None) is not None and parts.path != '':
-            _base_url = _base_url.replace(parts.path, "/")
+            _base_url = urlparse.urlunparse((parts.scheme,
+                                             parts.netloc,
+                                             '/',
+                                             parts.params,
+                                             parts.query,
+                                             parts.fragment))
 
         return _base_url
 
@@ -447,13 +458,24 @@
 
         parts = urlparse.urlparse(_base_url)
         if filters.get('api_version', None) is not None:
+            version_path = '/%s' % filters['api_version']
             path = re.sub(r'(^|/)+v\d+(?:\.\d+)?',
-                          '/' + filters['api_version'],
+                          version_path,
                           parts.path,
                           count=1)
-            _base_url = _base_url.replace(parts.path, path)
+            _base_url = urlparse.urlunparse((parts.scheme,
+                                             parts.netloc,
+                                             path or version_path,
+                                             parts.params,
+                                             parts.query,
+                                             parts.fragment))
         if filters.get('skip_path', None) is not None:
-            _base_url = _base_url.replace(parts.path, "/")
+            _base_url = urlparse.urlunparse((parts.scheme,
+                                             parts.netloc,
+                                             '/',
+                                             parts.params,
+                                             parts.query,
+                                             parts.fragment))
 
         return _base_url