diff --git a/tempest/api/volume/base.py b/tempest/api/volume/base.py
index ea3bb5a..107ff57 100644
--- a/tempest/api/volume/base.py
+++ b/tempest/api/volume/base.py
@@ -31,6 +31,11 @@
     """Base test case class for all Cinder API tests."""
 
     _api_version = 2
+    # if api_v2 is not enabled while api_v3 is enabled, the volume v2 classes
+    # should be transferred to volume v3 classes.
+    if (not CONF.volume_feature_enabled.api_v2 and
+        CONF.volume_feature_enabled.api_v3):
+        _api_version = 3
     credentials = ['primary']
 
     @classmethod
diff --git a/tempest/clients.py b/tempest/clients.py
index ca205c8..b06eafb 100644
--- a/tempest/clients.py
+++ b/tempest/clients.py
@@ -234,7 +234,9 @@
             self.volumes_client = self.volume_v1.VolumesClient()
             self.volumes_extension_client = self.volume_v1.ExtensionsClient()
 
-        if CONF.volume_feature_enabled.api_v2:
+        # if only api_v3 is enabled, all these clients should be available
+        if (CONF.volume_feature_enabled.api_v2 or
+            CONF.volume_feature_enabled.api_v3):
             self.backups_v2_client = self.volume_v2.BackupsClient()
             self.encryption_types_v2_client = \
                 self.volume_v2.EncryptionTypesClient()