src/Pure/PIDE/command.ML

   | exec_ids (SOME (eval, prints)) = eval_exec_id eval :: map print_exec_id prints;
 
 local
 
 fun run_print execution_id (Print {name, delay, pri, print_process, ...}) =
-  if Multithreading.enabled () orelse pri <= 0 then
+  if pri <= 0 orelse (Multithreading.enabled () andalso Options.default_bool "parallel_print")
+  then
     let
       val group = Future.worker_subgroup ();
       fun fork () =
         memo_fork {name = name, group = SOME group, deps = [], pri = pri, interrupts = true}
           execution_id print_process;