diff --git a/elnginx.go b/elnginx.go
index 24fa68e..47156ec 100644
--- a/elnginx.go
+++ b/elnginx.go
@@ -46,7 +46,7 @@ func addInstance(u config.Upstream, i *ec2.Instance) error {
 	u.Lock()
 	defer u.Unlock()
 
-	upstream := fmt.Sprintf("server %s:80 max_fails=3 fail_timeout=60s;\n", i.PrivateDNSName)
+	upstream := fmt.Sprintf("server %s:80 max_fails=3 fail_timeout=60s; # %s\n", i.PrivateDNSName, i.InstanceId)
 	buf := []byte(upstream)
 
 	if err := ioutil.WriteFile(filename, buf, 0640); err != nil {
diff --git a/elnginx_test.go b/elnginx_test.go
index 43ad127..6e00ef5 100644
--- a/elnginx_test.go
+++ b/elnginx_test.go
@@ -110,7 +110,7 @@ func (s *S) TestReadMessageWithLaunchJSON(c *gocheck.C) {
 	upstream := Config.Upstreams[0]
 	content, err := ioutil.ReadFile(upstream.File)
 	c.Assert(err, gocheck.IsNil)
-	serverLine := fmt.Sprintf("server %s.internal.invalid:80 max_fails=3 fail_timeout=60s;\n", s.instance_ids[0])
+	serverLine := fmt.Sprintf("server %s.internal.invalid:80 max_fails=3 fail_timeout=60s; # %s\n", s.instance_ids[0], s.instance_ids[0])
 	c.Assert(string(content), gocheck.Equals, fmt.Sprintf("upstream %s {\n  %s}\n", upstream.Name, serverLine))
 
 	// Check run NGINX reload
@@ -125,7 +125,7 @@ func (s *S) TestAddInstance(c *gocheck.C) {
 
 	content, err := ioutil.ReadFile(getUpstreamFilenameForInstance(u, i))
 	c.Assert(err, gocheck.IsNil)
-	c.Assert(string(content), gocheck.Equals, "server test.internal:80 max_fails=3 fail_timeout=60s;\n")
+	c.Assert(string(content), gocheck.Equals, "server test.internal:80 max_fails=3 fail_timeout=60s; # i-00000\n")
 }
 
 func (s *S) TestReadMessageWithTerminateJSON(c *gocheck.C) {