diff --git a/lib/utils/nexttick.js b/lib/utils/nexttick.js
index c45d4b92..365f5574 100644
--- a/lib/utils/nexttick.js
+++ b/lib/utils/nexttick.js
@@ -7,5 +7,8 @@
 'use strict';
 
 module.exports = function nextTick(handler) {
+  if (typeof handler !== 'function')
+    throw new Error('callback must be a function.');
+
   setImmediate(handler);
 };