diff --git a/builtin/providers/openstack/resource_openstack_compute_instance_v2.go b/builtin/providers/openstack/resource_openstack_compute_instance_v2.go
index 3101f41bc4..e30295e446 100644
--- a/builtin/providers/openstack/resource_openstack_compute_instance_v2.go
+++ b/builtin/providers/openstack/resource_openstack_compute_instance_v2.go
@@ -93,10 +93,11 @@ func resourceComputeInstanceV2() *schema.Resource {
 				},
 			},
 			"security_groups": &schema.Schema{
-				Type:     schema.TypeList,
+				Type:     schema.TypeSet,
 				Optional: true,
 				ForceNew: false,
 				Elem:     &schema.Schema{Type: schema.TypeString},
+				Set:      schema.HashString,
 			},
 			"availability_zone": &schema.Schema{
 				Type:     schema.TypeString,
@@ -600,9 +601,8 @@ func resourceComputeInstanceV2Update(d *schema.ResourceData, meta interface{}) e
 
 	if d.HasChange("security_groups") {
 		oldSGRaw, newSGRaw := d.GetChange("security_groups")
-		oldSGSlice, newSGSlice := oldSGRaw.([]interface{}), newSGRaw.([]interface{})
-		oldSGSet := schema.NewSet(func(v interface{}) int { return hashcode.String(v.(string)) }, oldSGSlice)
-		newSGSet := schema.NewSet(func(v interface{}) int { return hashcode.String(v.(string)) }, newSGSlice)
+		oldSGSet := oldSGRaw.(*schema.Set)
+		newSGSet := newSGRaw.(*schema.Set)
 		secgroupsToAdd := newSGSet.Difference(oldSGSet)
 		secgroupsToRemove := oldSGSet.Difference(newSGSet)
 
@@ -807,7 +807,7 @@ func ServerV2StateRefreshFunc(client *gophercloud.ServiceClient, instanceID stri
 }
 
 func resourceInstanceSecGroupsV2(d *schema.ResourceData) []string {
-	rawSecGroups := d.Get("security_groups").([]interface{})
+	rawSecGroups := d.Get("security_groups").(*schema.Set).List()
 	secgroups := make([]string, len(rawSecGroups))
 	for i, raw := range rawSecGroups {
 		secgroups[i] = raw.(string)