diff --git a/PyPowerFlex/base_client.py b/PyPowerFlex/base_client.py
index 352d343..7a30d4d 100644
--- a/PyPowerFlex/base_client.py
+++ b/PyPowerFlex/base_client.py
@@ -269,7 +269,11 @@ def get_api_version(self):
             dict: The JSON response containing the API version.
         """
         request_url = self.base_url + '/version'
-        self._login()
+        try:
+            self._appliance_login()
+        except exceptions.PowerFlexClientException as e:
+            LOG.error("Failed to login: %s. Revert to 3.x authentication.", e)
+            self._login()
         r = requests.get(request_url,
                          auth=(
                              self.configuration.username,
diff --git a/tests/common/__init__.py b/tests/common/__init__.py
index 7e4b68b..ef0c676 100644
--- a/tests/common/__init__.py
+++ b/tests/common/__init__.py
@@ -116,6 +116,7 @@ def decorator(subclass):
             '/login': 'token',
             VERSION_API_PATH: '4.5',
             '/logout': '',
+            '/rest/auth/login': {"access_token": "token", "refresh_token": "refresh_token"},
         },
         RESPONSE_MODE.Invalid: {
             VERSION_API_PATH: '2.5',
@@ -127,6 +128,12 @@ def decorator(subclass):
                     'message': 'Test login bad status',
                 }, 400
             ),
+            '/rest/auth/login': MockResponse(
+                {
+                    'errorCode': 1,
+                    'message': 'Test login bad status',
+                }, 400
+            ),
             '/version': MockResponse(
                 {
                     'errorCode': 2,
@@ -244,10 +251,8 @@ def get_mock_response(self, url, request_url=None, mode=None, *args, **kwargs):
 
         api_path = self.extract_path_segment(url, request_url)
         try:
-            if api_path == "/login":
-                response = self.RESPONSE_MODE.Valid[0]
-            elif api_path == "/logout":
-                response = self.RESPONSE_MODE.Valid[2]
+            if api_path in {"/login", "/rest/auth/login", "/logout"}:
+                response = self.DEFAULT_MOCK_RESPONSES[self.RESPONSE_MODE.Valid][api_path]
             else:
                 response = self.MOCK_RESPONSES[mode][api_path]
         except KeyError as e:
diff --git a/tests/gen1/test_system.py b/tests/gen1/test_system.py
index 9228d85..193bfed 100644
--- a/tests/gen1/test_system.py
+++ b/tests/gen1/test_system.py
@@ -100,7 +100,7 @@ def test_system_api_version(self):
         Test the API version.
         """
         self.client.system.api_version()
-        self.assertEqual(8, self.get_mock.call_count)
+        self.assertEqual(6, self.get_mock.call_count)
 
     def test_system_api_version_bad_status(self):
         """
@@ -127,7 +127,7 @@ def test_system_api_version_cached(self):
         self.client.system.api_version()
         self.client.system.api_version()
         self.client.system.api_version()
-        self.assertEqual(8, self.get_mock.call_count)
+        self.assertEqual(6, self.get_mock.call_count)
 
     def test_system_remove_cg_snapshots(self):
         """
diff --git a/tests/gen2/test_system.py b/tests/gen2/test_system.py
index 26bcbab..1bd3b18 100644
--- a/tests/gen2/test_system.py
+++ b/tests/gen2/test_system.py
@@ -97,7 +97,7 @@ def test_system_api_version(self):
         Test the API version.
         """
         self.client.system.api_version()
-        self.assertEqual(8, self.get_mock.call_count)
+        self.assertEqual(6, self.get_mock.call_count)
 
     def test_system_api_version_bad_status(self):
         """
@@ -124,7 +124,7 @@ def test_system_api_version_cached(self):
         self.client.system.api_version()
         self.client.system.api_version()
         self.client.system.api_version()
-        self.assertEqual(8, self.get_mock.call_count)
+        self.assertEqual(6, self.get_mock.call_count)
 
     def test_system_remove_cg_snapshots(self):
         """