diff --git a/src/Pure/System/isabelle_process.scala b/src/Pure/System/isabelle_process.scala
--- a/src/Pure/System/isabelle_process.scala
+++ b/src/Pure/System/isabelle_process.scala
@@ -1,82 +1,82 @@
 /*  Title:      Pure/System/isabelle_process.scala
     Author:     Makarius
 
 Isabelle process wrapper.
 */
 
 package isabelle
 
 
 import java.io.{File => JFile}
 
 
 object Isabelle_Process
 {
   def start(
     session: Session,
     options: Options,
     sessions_structure: Sessions.Structure,
     store: Sessions.Store,
     logic: String = "",
     raw_ml_system: Boolean = false,
     use_prelude: List[String] = Nil,
     eval_main: String = "",
     modes: List[String] = Nil,
     cwd: JFile = null,
     env: Map[String, String] = Isabelle_System.settings()): Isabelle_Process =
   {
     val channel = System_Channel()
     val process =
       try {
         val channel_options =
           options.string.update("system_channel_address", channel.address).
             string.update("system_channel_password", channel.password)
         ML_Process(channel_options, sessions_structure, store,
           logic = logic, raw_ml_system = raw_ml_system,
           use_prelude = use_prelude, eval_main = eval_main,
           modes = modes, cwd = cwd, env = env)
       }
       catch { case exn @ ERROR(_) => channel.shutdown(); throw exn }
-    process.stdin.close()
 
     val isabelle_process = new Isabelle_Process(session, process)
+    process.stdin.close()
     session.start(receiver => new Prover(receiver, session.cache, channel, process))
 
     isabelle_process
   }
 }
 
 class Isabelle_Process private(session: Session, process: Bash.Process)
 {
   private val startup = Future.promise[String]
   private val terminated = Future.promise[Process_Result]
 
   session.phase_changed +=
     Session.Consumer(getClass.getName) {
       case Session.Ready =>
         startup.fulfill("")
       case Session.Terminated(result) =>
         if (!result.ok && !startup.is_finished) {
           val syslog = session.syslog_content()
           val err = "Session startup failed" + (if (syslog.isEmpty) "" else ":\n" + syslog)
           startup.fulfill(err)
         }
         terminated.fulfill(result)
       case _ =>
     }
 
   def await_startup(): Isabelle_Process =
     startup.join match {
       case "" => this
       case err => session.stop(); error(err)
     }
 
   def await_shutdown(): Process_Result =
   {
     val result = terminated.join
     session.stop()
     result
   }
 
   def terminate(): Unit = process.terminate()
 }