I have a Magento 2 Installation in which everything appears to be working fine except products will not add to the cart. The add to cart button appears to do nothing at all. I am getting the following error in console from knockout.js file line:3012

Uncaught TypeError: Unable to process binding "css: function (){return { empty:cart().summary_count == 0} }"
Message: cart is not a function

Has anyone experienced anything similar? I cannot find any documentation on similar issues with Magento2.


  • 2
    Hi Daniel, do you have customizations, css changes, js changes? Do you use development mode? Please clarify. thanks
    – Max Pronko
    Commented Jan 15, 2016 at 19:26
  • What's the version of magento you use? Did you have magento 2 previously installed on this domain? Did you clear browser cache?
    – Anton Kril
    Commented Jan 16, 2016 at 9:28
  • @MaxPronko Yes! A piece of JavaScript in a custom theme was causing the issue. Thanks.
    – Daniel
    Commented Jan 18, 2016 at 16:32

1 Answer 1


This was solved. Some unknown JavaScript in a custom theme was clashing with some part of the Add to Cart process. I reverted to a default theme and the issue was resolved.

  • Its been a while, but could you clarify which JS exactly destroyed knockout.js? Am having the same issue and struggeling to find that JS code.
    – Max
    Commented Sep 13, 2016 at 8:44
  • @Max Apologies Max, but I don't remember. It was nothing within an existing Magento theme, only some minor functionality I had implemented to show/hide elements if I remember correctly. Be sure to use .noConflict. Good luck!
    – Daniel
    Commented Sep 14, 2016 at 12:13

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