diff --git a/lib/index.ts b/lib/index.ts
index adf83788..5a4ace28 100644
--- a/lib/index.ts
+++ b/lib/index.ts
@@ -75,7 +75,7 @@ export default class Backburner {
     platform.clearTimeout = _platform.clearTimeout || ((id) => clearTimeout(id));
     platform.next = _platform.next || ((fn) => platform.setTimeout(fn, 0));
     platform.clearNext = _platform.clearNext || platform.clearTimeout;
-    platform.now = _platform.now || Date.now;
+    platform.now = _platform.now || (() => Date.now());
 
     this._platform = platform;
 
diff --git a/tests/set-timeout-test.ts b/tests/set-timeout-test.ts
index d59cbf0d..5a17c31b 100644
--- a/tests/set-timeout-test.ts
+++ b/tests/set-timeout-test.ts
@@ -50,17 +50,20 @@ QUnit.test('later', function(assert) {
   }, 20);
 });
 
-QUnit.test('later can continue when `Date.now` is monkey-patched', function(assert) {
+QUnit.test('later should rely on stubbed `Date.now`', function(assert) {
   assert.expect(1);
 
-  let arbitraryTime = +new Date();
   let bb = new Backburner(['one']);
   let done = assert.async();
+  let globalNowWasUsed = false;
 
-  Date.now = function() { return arbitraryTime; };
+  Date.now = function() {
+    globalNowWasUsed = true;
+    return originalDateNow();
+  };
 
   bb.later(() => {
-    assert.ok(true);
+    assert.ok(globalNowWasUsed);
     done();
   }, 1);
 });