diff --git a/tempest/services/compute/v3/json/flavors_client.py b/tempest/services/compute/v3/json/flavors_client.py
index e99ac91..a790c40 100644
--- a/tempest/services/compute/v3/json/flavors_client.py
+++ b/tempest/services/compute/v3/json/flavors_client.py
@@ -61,7 +61,7 @@
             'id': flavor_id,
         }
         if kwargs.get('ephemeral'):
-            post_body['OS-FLV-EXT-DATA:ephemeral'] = kwargs.get('ephemeral')
+            post_body['ephemeral'] = kwargs.get('ephemeral')
         if kwargs.get('swap'):
             post_body['swap'] = kwargs.get('swap')
         if kwargs.get('rxtx'):