diff --git a/lib/timers.js b/lib/timers.js
index aa9f316253e692..5a0a8ab271e549 100644
--- a/lib/timers.js
+++ b/lib/timers.js
@@ -23,14 +23,17 @@ const TIMEOUT_MAX = 2147483647; // 2^31-1
 // value = list
 var lists = {};
 
+
+// call this whenever the item is active (not idle)
+// it will reset its timeout.
 // the main function - creates lists on demand and the watchers associated
 // with them.
-function insert(item, msecs) {
-  item._idleStart = Timer.now();
-  item._idleTimeout = msecs;
-
+exports.active = function(item) {
+  const msecs = item._idleTimeout;
   if (msecs < 0) return;
 
+  item._idleStart = Timer.now();
+
   var list;
 
   if (lists[msecs]) {
@@ -48,7 +51,7 @@ function insert(item, msecs) {
 
   L.append(list, item);
   assert(!L.isEmpty(list)); // list is not empty
-}
+};
 
 function listOnTimeout() {
   var msecs = this.msecs;
@@ -156,15 +159,6 @@ exports.enroll = function(item, msecs) {
 };
 
 
-// call this whenever the item is active (not idle)
-// it will reset its timeout.
-exports.active = function(item) {
-  var msecs = item._idleTimeout;
-  if (msecs >= 0)
-    insert(item, msecs);
-};
-
-
 /*
  * DOM-style timers
  */
diff --git a/test/parallel/test-timers-active.js b/test/parallel/test-timers-active.js
new file mode 100644
index 00000000000000..9162406848d195
--- /dev/null
+++ b/test/parallel/test-timers-active.js
@@ -0,0 +1,33 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const active = require('timers').active;
+
+// active() should create timers for these
+var legitTimers = [
+  { _idleTimeout: 0 },
+  { _idleTimeout: 1 }
+];
+
+legitTimers.forEach(function(legit) {
+  const savedTimeout = legit._idleTimeout;
+  active(legit);
+  // active() should mutate these objects
+  assert(legit._idleTimeout === savedTimeout);
+  assert(Number.isInteger(legit._idleStart));
+  assert(legit._idleNext);
+  assert(legit._idlePrev);
+});
+
+
+// active() should not create a timer for these
+var bogusTimers = [
+  { _idleTimeout: -1 }
+];
+
+bogusTimers.forEach(function(bogus) {
+  const savedTimeout = bogus._idleTimeout;
+  active(bogus);
+  // active() should not mutate these objects
+  assert.deepStrictEqual(bogus, {_idleTimeout: savedTimeout});
+});