diff --git a/server.js b/server.js
index 10eb839..f0db1f0 100644
--- a/server.js
+++ b/server.js
@@ -15,6 +15,8 @@ const parseHttpRequest = require('./lib/server/parse-http')
 const parseUdpRequest = require('./lib/server/parse-udp')
 const parseWebSocketRequest = require('./lib/server/parse-websocket')
 
+const hasOwnProperty = Object.prototype.hasOwnProperty
+
 /**
  * BitTorrent tracker server.
  *
@@ -147,7 +149,7 @@ class Server extends EventEmitter {
           let key
 
           for (key in allPeers) {
-            if (allPeers.hasOwnProperty(key) && filterFunction(allPeers[key])) {
+            if (hasOwnProperty.call(allPeers, key) && filterFunction(allPeers[key])) {
               count++
             }
           }
@@ -158,7 +160,7 @@ class Server extends EventEmitter {
         function groupByClient () {
           const clients = {}
           for (const key in allPeers) {
-            if (allPeers.hasOwnProperty(key)) {
+            if (hasOwnProperty.call(allPeers, key)) {
               const peer = allPeers[key]
 
               if (!clients[peer.client.client]) {
@@ -179,10 +181,10 @@ class Server extends EventEmitter {
         function printClients (clients) {
           let html = '<ul>\n'
           for (const name in clients) {
-            if (clients.hasOwnProperty(name)) {
+            if (hasOwnProperty.call(clients, name)) {
               const client = clients[name]
               for (const version in client) {
-                if (client.hasOwnProperty(version)) {
+                if (hasOwnProperty.call(client, version)) {
                   html += `<li><strong>${name}</strong> ${version} : ${client[version]}</li>\n`
                 }
               }
@@ -203,7 +205,7 @@ class Server extends EventEmitter {
               const peer = peers.peek(peerId)
               if (peer == null) return // peers.peek() can evict the peer
 
-              if (!allPeers.hasOwnProperty(peerId)) {
+              if (!hasOwnProperty.call(allPeers, peerId)) {
                 allPeers[peerId] = {
                   ipv4: false,
                   ipv6: false,