Accordion is messed up on page but works in preview - javascript wrapping problem

I installed the module and noticed that while the accordion was created fine in preview, it was messed up on the actual page. After some troubleshooting I found that the problem came from these lines in views-accordion.js:

            // Wrap the accordion content within a div if necessary
            if (!usegroupheader) {
              $this.siblings().wrapAll('<div></div>');
            }

It seemed to me that the wrapping should be made IF a group header is used, not if it is not used. Therefore I tried removing the exclamation mark so that the code looked like this instead:

           // Wrap the accordion content within a div if necessary
            if (usegroupheader) {
              $this.siblings().wrapAll('<div></div>');
            }

That fixed the problem for me.