Asp.net Web API returns non-descriptive error 500

In my setup I get error 500 if anything goes wrong with my Web API request.

For instance with this simple code.

public IQueryable<Article> Get(){
    throw new Exception("error");
    return db.Articles; //yeah i know.. unreachable, not the point
}

What I expect(and what happens in a regular MVC controller):

What I get (in Web API):

My web config:

<customErrors mode="Off"/>
<compilation debug="true" targetFramework="4.5">

//under webserver
<httpErrors errorMode="detailed"/>

The app pool is running 4.0 in integrated mode. 32-bit applications are enabled.

How can I get the error to surface in the browser? Or at the very least during debugging?