https://lists.gnu.org/archive/html/bug-bash/2015-07/msg00060.html

*** ../bash-4.4-alpha/execute_cmd.c	2015-06-12 17:29:18.000000000 -0400
--- execute_cmd.c	2015-07-14 08:59:22.000000000 -0400
***************
*** 2630,2638 ****
  	  if (ignore_return && second)
  	    second->flags |= CMD_IGNORE_RETURN;
- 	  if (should_suppress_fork (second))
- 	    {
- 	      second->flags |= CMD_NO_FORK;
- 	      second->value.Simple->flags |= CMD_NO_FORK;
- 	    }
  
  	  exec_result = execute_command (second);
--- 2630,2633 ----