diff --git a/openstack/compute/v2/extensions/servergroups/results.go b/openstack/compute/v2/extensions/servergroups/results.go
index ff64a7e..ab49b35 100644
--- a/openstack/compute/v2/extensions/servergroups/results.go
+++ b/openstack/compute/v2/extensions/servergroups/results.go
@@ -37,12 +37,11 @@
 
 // ExtractServerGroups interprets a page of results as a slice of
 // ServerGroups.
-func ExtractServerGroups(page pagination.Page) ([]ServerGroup, error) {
-	r := page.(ServerGroupPage)
+func ExtractServerGroups(r pagination.Page) ([]ServerGroup, error) {
 	var s struct {
 		ServerGroups []ServerGroup `json:"server_groups"`
 	}
-	err := r.ExtractInto(&s)
+	err := (r.(ServerGroupPage)).ExtractInto(&s)
 	return s.ServerGroups, err
 }