src/Pure/System/command_line.scala

               Output.error_message(Exn.print(exn))
               Exn.failure_rc(exn)
           }
         sys.exit(rc)
       }
-    thread.join
+    thread.join()
   }
 
   def ML_tool(body: List[String]): String =
     "Command_Line.tool (fn () => (" + body.mkString("; ") + "));"
 }