diff --git a/tempest/api/compute/admin/test_flavors_negative.py b/tempest/api/compute/admin/test_flavors_negative.py
index 3389aee..5bc3d10 100644
--- a/tempest/api/compute/admin/test_flavors_negative.py
+++ b/tempest/api/compute/admin/test_flavors_negative.py
@@ -58,7 +58,7 @@
         resp, flavor = self.client.create_flavor(flavor_name,
                                                  self.ram,
                                                  self.vcpus, self.disk,
-                                                 '',
+                                                 None,
                                                  ephemeral=self.ephemeral,
                                                  swap=self.swap,
                                                  rxtx=self.rxtx)