diff --git a/README.md b/README.md
new file mode 100644
index 0000000..c8ddd3c
--- /dev/null
+++ b/README.md
@@ -0,0 +1,4 @@
+Requires
+	proxy_set_header X-Real-IP $remote_addr;
+in nginx server config
+
diff --git a/main.go b/main.go
index 3a9cb9f..a2194d7 100644
--- a/main.go
+++ b/main.go
@@ -61,6 +61,9 @@ func listen(listenPort, proxyPort int) {
 func filter(res http.ResponseWriter, req *http.Request, listenPort, proxyPort int) {
 	ip := req.RemoteAddr
 
+	// requires
+	// proxy_set_header X-Real-IP $remote_addr;
+	// in nginx server config
 	if realIp := req.Header.Get("X-Real-IP"); realIp != "" {
 		ip = realIp
 	}