`render :nothing => true` whines about "missing template".

It’s hard to know without seeing a code sample. Perhaps your render call is lurking within a conditional?

Note that in 1.2 you can do “head 204” or “head :no_content” when you have nothing to render and just want to return a status and optional headers. The symbolic status code is translated to 204 No Content (likewise for head :forbidden, head :whatever_status_code, etc.)