Server Side Include and trailing slashes - not being 404

I have a site on IIS 10 that uses server side include directives.  It works great except one thing.

<!--#include file="hours.html"-->

If i go to any url of my page, such http://www.site.com/index.html  -  this works.

But if i go to www.site.com/index.html/foo   - this should be a broken link but instead it returns the index.html with all of the relative paths wrong (css and js broken). It should be a 404 correct?   I think i want it to be a 404.   Problem is google custom search is finding a bunch of these  index.html/foo type links.

The problem goes away if i disable server side include.  Any assistance would be appreciated.