Maintenance Page URI issue

I have an irule thats working as expected when the pool is down and does throw the maintenance page exactly how i expected. But when the URI is added the irule fails to load at all

{works} {fails}

Does anyone have any clue as to why its not working?

Code
  when LB_FAILED {
     switch [HTTP::uri] {
       "/error.css" {
       HTTP::respond 200 content [ifile get "error"] "Content-Type" "text/css"
       return
       }
      "/logo.png" {
      HTTP::respond 200 content [ifile get "logo"] "Content-Type" "image/png"
      return
      }
   }
   HTTP::respond 200 content [ifile get "maint"] "Content-Type" "text/html"
 }