Constructor not found / invalid template errors

Hi all, Out of the blue we get custom widget related errors within applications that aren't changed with a new Mendix or application version. The only thing that happened is probably a restart of the cloud node. In several projects we get these errors, today. I think it's way to specific (multiple project, multiple people, all today) for a coincidence. So just wondering if anybody else experience this error..
4 answers

Are you getting this in chrome, or other browsers as well? If you're using chrome 48, you might be running into this issue.

If our theory is correct and it is the chromium issue I mentioned above, you can use the following patch:

(function() {
    if (parseInt(navigator.userAgent.split("Chrome/")[1]) !== 48) return;
    var openReal =; = function(method, url, async, user, password) {
        if (!async) url += (/\?/.test(url) ? "&" : "?") + new Date().getTime();, method, url, async, user, password);

in your index.html which fixes the issue. The latest chrome 48 stable (which was released 02-03-2016) includes a fix. (thanks @andriessmit for mentioning this, including this information here for completeness sake)


To answer Herbert's original question; yes, also see this same thing happening for an application, so does not seem like a coincidence.


I have these errors when working on different projects and Menix versions. Browser gets a little confused sometimes. Hitting ctrl-F5 usually solves it. Sometmes I need to manually clean the browser cache and restart the browser.


This bug is already fixed in Chromium,

It is expected to moving solved soon in Chrome.

To Test if this issue is fixed:

Test steps:

  1. load the given url:
  2. alert is shown "All is well."
  3. press F5 (refresh page)
  4. alert is shown "Second Empty is empty !!


Thanks to Joost Stapersma and Diego Slijkhuis

Cheers, Andries