diff --git a/index.js b/index.js
index <HASH>..<HASH> 100644
--- a/index.js
+++ b/index.js
@@ -5,6 +5,10 @@ var _ = require('lodash');
 function changed(Model, options) {
   'use strict';
 
+  if(typeof Model[options.callback] !== 'function') {
+    console.warn('Callback %s is not a model function', options.callback);
+  }
+
   debug('Changed mixin for Model %s', Model.modelName);
 
   var loopback = require('loopback');
@@ -68,6 +72,7 @@ function changed(Model, options) {
           Model.getIdName()
         ]
       }).then(function(items) {
+        if(typeof Model[options.callback] !== 'function') return false;
         return Model[options.callback](Model.extractChangedItemIds(items));
       })
       .then(function(res) {
Add warning and skip execution if callback function is not defined