Need help with WMS!

After I include a WMS layer I get an error after i click on map.
The code works fine on the Cesium live code editor, I only get this error locally.

If anyone can help me with that issue I’d really appreciate.

Here is the error i get :
And here is how i load the WMS layer :

This was a bug in 1.7 that was quickly fixed in 1.7.1. Are you using the latest version?

I was using 1.7, i thought i had problem in the code somewhere, I’m using 1.7.1 now and it’s working fine.

Thank you very much!