diff --git a/setup.cfg b/setup.cfg
index 782b3ef97..652e9a91e 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -90,6 +90,7 @@ nova.api.v3.extensions =
     hypervisors = nova.api.openstack.compute.plugins.v3.hypervisors:Hypervisors
     images = nova.api.openstack.compute.plugins.v3.images:Images
     image_metadata = nova.api.openstack.compute.plugins.v3.image_metadata:ImageMetadata
+    image_size = nova.api.openstack.compute.plugins.v3.image_size:ImageSize
     instance_actions = nova.api.openstack.compute.plugins.v3.instance_actions:InstanceActions
     ips = nova.api.openstack.compute.plugins.v3.ips:IPs
     keypairs = nova.api.openstack.compute.plugins.v3.keypairs:Keypairs