diff --git a/lib/timers.js b/lib/timers.js
index 2ef3e32da9a26e..35f9ddee0bd158 100644
--- a/lib/timers.js
+++ b/lib/timers.js
@@ -24,24 +24,23 @@ var triggerTimers = new Map();
 // the main function - creates lists on demand and the watchers associated
 // with them.
 function insert(item, msecs) {
-  item._idleStart = Timer.now();
-  item._idleTimeout = msecs;
-
   if (msecs < 0) return;
 
-  var timer;
-
-  if (! lists[msecs]) {
-    timer = new Timer();
-    timer.start(msecs, 0);
-    timer.msecs = msecs;
-    timer[kOnTimeout] = listOnTimeout;
+  item._idleStart = Timer.now();
+  item._idleTimeout = msecs;
 
-    lists[msecs] = new Set();
-    triggerTimers.set(msecs, timer);
+  if (lists[msecs]) {
+    lists[msecs].add(item);
+    return;
   }
 
-  lists[msecs].add(item);
+  lists[msecs] = new Set().add(item);
+
+  const timer = new Timer();
+  timer.start(msecs, 0);
+  timer.msecs = msecs;
+  timer[kOnTimeout] = listOnTimeout;
+  triggerTimers.set(msecs, timer);
 }
 
 function listOnTimeout() {
@@ -51,53 +50,54 @@ function listOnTimeout() {
   var now = Timer.now();
 
   var diff, first, threw;
-  if (lists[msecs]) {
-    for (let first of lists[msecs]) {
-      diff = now - first._idleStart;
-      if (diff < msecs) {
-        list.start(msecs - diff, 0);
-        return;
-      } else {
-        lists[msecs].delete(first);
-        if (!first._onTimeout) continue;
-
-        // v0.4 compatibility: if the timer callback throws and the
-        // domain or uncaughtException handler ignore the exception,
-        // other timers that expire on this tick should still run.
-        //
-        // https://github.com/joyent/node/issues/2631
-        var domain = first.domain;
-        if (domain && domain._disposed)
-          continue;
-
-        try {
-          if (domain)
-            domain.enter();
-          threw = true;
-          first._called = true;
-          first._onTimeout();
-          if (domain)
-            domain.exit();
-          threw = false;
-        } finally {
-          if (threw) {
-            // We need to continue processing after domain error handling
-            // is complete, but not by using whatever domain was left over
-            // when the timeout threw its exception.
-            var oldDomain = process.domain;
-            process.domain = null;
-            process.nextTick(listOnTimeoutNT, list);
-            process.domain = oldDomain;
-          }
+  for (let first of lists[msecs]) {
+    diff = now - first._idleStart;
+    if (diff < msecs) {
+      list.start(msecs - diff, 0);
+      return;
+    } else {
+      lists[msecs].delete(first);
+      if (!first._onTimeout) continue;
+
+      // v0.4 compatibility: if the timer callback throws and the
+      // domain or uncaughtException handler ignore the exception,
+      // other timers that expire on this tick should still run.
+      //
+      // https://github.com/joyent/node/issues/2631
+      var domain = first.domain;
+      if (domain && domain._disposed)
+        continue;
+
+      try {
+        if (domain)
+          domain.enter();
+
+        threw = true;
+        first._called = true;
+        first._onTimeout();
+
+        if (domain)
+          domain.exit();
+
+        threw = false;
+      } finally {
+        if (threw) {
+          // We need to continue processing after domain error handling
+          // is complete, but not by using whatever domain was left over
+          // when the timeout threw its exception.
+          var oldDomain = process.domain;
+          process.domain = null;
+          process.nextTick(listOnTimeoutNT, list);
+          process.domain = oldDomain;
         }
       }
     }
   }
-
-  list.close();
   if (lists[msecs] && lists[msecs].size === 0) {
     delete lists[msecs];
   }
+
+  list.close();
 }
 
 
@@ -530,7 +530,7 @@ function unrefTimeout() {
   // call the onTimeout callback for those expired,
   // and rearm the actual timer if the next timeout to expire
   // will expire before the current actual timer.
-  for (var cur of unrefList) {
+  for (let cur of unrefList) {
     timeSinceLastActive = now - cur._idleStart;
 
     if (timeSinceLastActive < cur._idleTimeout) {