creat Custom Board problem

i use mk_taget_board cmd to creat my custome board ,but it appears this error.

software verson 5.1

enter the cmd in NIOS II SDK SHELL：

[SOPC Builder]$ mk_target_board --name=Hard_Board_2c5 --family=CycloneII

--clock=22.1184 --index=1

--buffer_size=2048

--class=name=Hard_Board_CycloneII_2c5

--epcs=U6

output the results in screen：

Make Target Board version 1.01

Switch summary:

Board name: "Hard_Board_2c5"

Board class: Hard_Board_CycloneII_2c5

Device family: "Cyclone II"

Clock frequency: 22118400hz

Payload buffer size: 2048 bytes

EPCS flash enabled with reference designator:U6

ERROR:

c:/altera/kits/nios2_51/bin/create-board.pl 1279 CALLED (main)

c:/altera/kits/nios2_51/bin/create-board.pl 99 CALLED (cb_setup_directories)

c:/altera/kits/nios2_51/bin/create-board.pl 511 CALLED(europa_utils::find_component_dir)

/cygdrive/c/altera/quartus51/sopc_builder/bin/europa/europa_utils.pm 2030 CALLED

(europa_utils::ensure_class_ptfs)WHERE

‘get_class_ptg and ensure_class_ptfs must be called with g{system_directory}’OCCURRED on

/cygdrive/c/altera/quartus51/sopc_builder/bin/europa/europa_utils.pm 1923