User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/48.0.2564.116 Safari/537.36 Steps to reproduce: plain_text is: content_type 'text/plain' 'This is text/plain' -> POST session/838c7f98-223b-6b46-b953-c5eed1d18912/url >>> http://127.0.0.1:4444/session/838c7f98-223b-6b46-b953-c5eed1d18912/url | {"url":"file:///Users/tfortner/git/watir_temp/watir-webdriver/spec/watirspec/html/plain_text"} > {"Accept"=>"application/json", "Content-Type"=>"application/json; charset=utf-8", "Content-Length"=>"94"} 1457737278722 Marionette TRACE conn0 -> [0,2,"get",{"url":"file:///Users/tfortner/git/watir_temp/watir-webdriver/spec/watirspec/html/plain_text"}] 1457737278820 Marionette TRACE conn0 <- [1,2,{"error":"unknown error","message":"Error loading page","stacktrace":null},null] <- {"error":"unknown error","message":"Error loading page"} Actual results: raised unknown error message Expected results: All other drivers raise UnknownObjectException when trying to access DOM elements on plain/text-page

It's worth adding that the specification isn't entirely clear on how to handle documents of a different doctype than HTML, and this should also be fixed.

This appears to work in Nightly now, probably due to whimboo’s recent page load algorithm changes.