ASP.NET 4 Routing querystrings problems

Question

I have an ASP.NET 4 WebForms Web Application which is using Routing. I have URL's like this:

http://website.com/product/123/name

To use querystrings I made this route:

product/{pid}/{name}/{*queryvalues}

And I thought, instead of using normal querystrings like ?queryitem=value&item2=value2 I made this:

http://website.com/product/123/name/category-12/

Where category-12 is a querystring like ?category=12

But now my page Init event is fired twice, it seems like it treats the querystring as a separate page. Why is this? How can this be avoided, reverting back to normal querystrings?