diff --git a/oslo_vmware/api.py b/oslo_vmware/api.py
index df68bc9..dabc461 100644
--- a/oslo_vmware/api.py
+++ b/oslo_vmware/api.py
@@ -321,7 +321,8 @@ class VMwareAPISession(object):
                         LOG.debug("Fault list: %s", excep.fault_list)
                         fault = excep.fault_list[0]
                         clazz = exceptions.get_fault_class(fault)
-                        raise clazz(six.text_type(excep), excep.details)
+                        if clazz:
+                            raise clazz(six.text_type(excep), excep.details)
                     raise
 
             except exceptions.VimConnectionException:
@@ -413,7 +414,12 @@ class VMwareAPISession(object):
                 error_msg = six.text_type(task_info.error.localizedMessage)
                 error = task_info.error
                 name = error.fault.__class__.__name__
-                task_ex = exceptions.get_fault_class(name)(error_msg)
+                fault_class = exceptions.get_fault_class(name)
+                if fault_class:
+                    task_ex = fault_class(error_msg)
+                else:
+                    task_ex = exceptions.VimFaultException([name],
+                                                           error_msg)
                 raise task_ex
 
     def wait_for_lease_ready(self, lease):
diff --git a/oslo_vmware/exceptions.py b/oslo_vmware/exceptions.py
index 039be05..cd53319 100644
--- a/oslo_vmware/exceptions.py
+++ b/oslo_vmware/exceptions.py
@@ -254,7 +254,6 @@ def get_fault_class(name):
     fault_class = _fault_classes_registry.get(name)
     if not fault_class:
         LOG.debug('Fault %s not matched.', name)
-        fault_class = VMwareDriverException
     return fault_class
 
 
diff --git a/oslo_vmware/tests/test_api.py b/oslo_vmware/tests/test_api.py
index d0459b6..31120bf 100644
--- a/oslo_vmware/tests/test_api.py
+++ b/oslo_vmware/tests/test_api.py
@@ -373,6 +373,19 @@ class VMwareAPISessionTest(base.TestCase):
             userName=api_session._session_username)
         api_session._create_session.assert_called_once_with()
 
+    def test_invoke_api_with_unknown_fault(self):
+        api_session = self._create_api_session(True)
+        fault_list = ['NotAFile']
+
+        module = mock.Mock()
+        module.api.side_effect = exceptions.VimFaultException(fault_list,
+                                                              'Not a file.')
+        ex = self.assertRaises(exceptions.VimFaultException,
+                               api_session.invoke_api,
+                               module,
+                               'api')
+        self.assertEqual(fault_list, ex.fault_list)
+
     def test_wait_for_task(self):
         api_session = self._create_api_session(True)
         task_info_list = [('queued', 0), ('running', 40), ('success', 100)]
@@ -413,7 +426,7 @@ class VMwareAPISessionTest(base.TestCase):
         api_session.invoke_api = mock.Mock(side_effect=invoke_api_side_effect)
         task = mock.Mock()
         with mock.patch.object(greenthread, 'sleep'):
-            self.assertRaises(exceptions.VMwareDriverException,
+            self.assertRaises(exceptions.VimFaultException,
                               api_session.wait_for_task,
                               task)
         api_session.invoke_api.assert_called_with(vim_util,
@@ -531,8 +544,8 @@ class VMwareAPISessionTest(base.TestCase):
 
     def test_poll_task_unknown_exception(self):
         _unknown_exceptions = {
-            'NotAFile': exceptions.VMwareDriverException,
-            'RuntimeFault': exceptions.VMwareDriverException
+            'NotAFile': exceptions.VimFaultException,
+            'RuntimeFault': exceptions.VimFaultException
         }
 
         for k, v in six.iteritems(_unknown_exceptions):
diff --git a/oslo_vmware/tests/test_exceptions.py b/oslo_vmware/tests/test_exceptions.py
index 2cf2462..46c3660 100644
--- a/oslo_vmware/tests/test_exceptions.py
+++ b/oslo_vmware/tests/test_exceptions.py
@@ -107,5 +107,4 @@ class ExceptionsTest(base.TestCase):
         self.assertEqual(exceptions.NoDiskSpaceException,
                          exceptions.get_fault_class("NoDiskSpace"))
         # Test unknown fault.
-        self.assertEqual(exceptions.VMwareDriverException,
-                         exceptions.get_fault_class("NotAFile"))
+        self.assertIsNone(exceptions.get_fault_class("NotAFile"))
diff --git a/tests/test_api.py b/tests/test_api.py
index 8d18f92..ebf83c0 100644
--- a/tests/test_api.py
+++ b/tests/test_api.py
@@ -412,7 +412,7 @@ class VMwareAPISessionTest(base.TestCase):
         api_session.invoke_api = mock.Mock(side_effect=invoke_api_side_effect)
         task = mock.Mock()
         with mock.patch.object(greenthread, 'sleep'):
-            self.assertRaises(exceptions.VMwareDriverException,
+            self.assertRaises(exceptions.VimFaultException,
                               api_session.wait_for_task,
                               task)
         api_session.invoke_api.assert_called_with(new_vim_util,
@@ -526,8 +526,8 @@ class VMwareAPISessionTest(base.TestCase):
 
     def test_poll_task_unknown_exception(self):
         _unknown_exceptions = {
-            'NoDiskSpace': exceptions.VMwareDriverException,
-            'RuntimeFault': exceptions.VMwareDriverException
+            'NotAFile': exceptions.VimFaultException,
+            'RuntimeFault': exceptions.VimFaultException
         }
 
         for k, v in six.iteritems(_unknown_exceptions):