src/Pure/Thy/document_build.scala

 
       isabelle_logo.foreach(_.write(doc_dir))
       session_graph.write(doc_dir)
 
       if (verbose) {
-        progress.bash("ls -alR", echo = true, cwd = doc_dir.file).check
+        progress.bash("ls -alR", echo = true, cwd = doc_dir).check
         progress match {
           case program_progress: Program_Progress => program_progress.stop_program()
           case _ =>
         }
       }

     ): Document_Output = {
       val progress = context.progress
       val result =
         progress.bash(
           build_script(context, directory),
-          cwd = directory.doc_dir.file,
+          cwd = directory.doc_dir,
           echo = verbose,
           watchdog = Time.seconds(0.5))
 
       val log = result.out_lines ::: result.err_lines
       val err = result.err