*** a/src/backend/replication/walsender.c
--- b/src/backend/replication/walsender.c
***************
*** 476,482 ****
  	if (MyWalSnd == NULL)
  		ereport(FATAL,
  				(errcode(ERRCODE_TOO_MANY_CONNECTIONS),
! 				 errmsg("sorry, too many standbys already")));
  
  	/* Arrange to clean up at walsender exit */
  	on_shmem_exit(WalSndKill, 0);
--- 476,483 ----
  	if (MyWalSnd == NULL)
  		ereport(FATAL,
  				(errcode(ERRCODE_TOO_MANY_CONNECTIONS),
! 				 errmsg("number of requested standby connections"
! 					"exceeds max_wal_senders (currently %d)", i + 1)));
  
  	/* Arrange to clean up at walsender exit */
  	on_shmem_exit(WalSndKill, 0);