===================================================================
RCS file: /cvsrepo/anoncvs/cvs/src/usr.bin/tmux/cmd-attach-session.c,v
retrieving revision 1.34
retrieving revision 1.35
diff -c -r1.34 -r1.35
*** src/usr.bin/tmux/cmd-attach-session.c	2015/04/25 18:09:28	1.34
--- src/usr.bin/tmux/cmd-attach-session.c	2015/06/04 23:27:51	1.35
***************
*** 1,4 ****
! /* $OpenBSD: cmd-attach-session.c,v 1.34 2015/04/25 18:09:28 nicm Exp $ */
  
  /*
   * Copyright (c) 2007 Nicholas Marriott <nicm@users.sourceforge.net>
--- 1,4 ----
! /* $OpenBSD: cmd-attach-session.c,v 1.35 2015/06/04 23:27:51 nicm Exp $ */
  
  /*
   * Copyright (c) 2007 Nicholas Marriott <nicm@users.sourceforge.net>
***************
*** 36,42 ****
  	"attach-session", "attach",
  	"c:drt:", 0, 0,
  	"[-dr] [-c working-directory] " CMD_TARGET_SESSION_USAGE,
! 	CMD_CANTNEST|CMD_STARTSERVER,
  	cmd_attach_session_exec
  };
  
--- 36,42 ----
  	"attach-session", "attach",
  	"c:drt:", 0, 0,
  	"[-dr] [-c working-directory] " CMD_TARGET_SESSION_USAGE,
! 	CMD_STARTSERVER,
  	cmd_attach_session_exec
  };
  
***************
*** 81,86 ****
--- 81,91 ----
  
  	if (cmdq->client == NULL)
  		return (CMD_RETURN_NORMAL);
+ 	if (server_client_check_nested(cmdq->client)) {
+ 		cmdq_error(cmdq, "sessions should be nested with care, "
+ 		    "unset $TMUX to force");
+ 		return (CMD_RETURN_ERROR);
+ 	}
  
  	if (wl != NULL) {
  		if (wp != NULL)