OsmocomBB

when i excute the command ：sudo ./ccch_scan -i 127.0.0.1 -a 50. i got the error msg. below is error msg detail.
Assert failed l2_len == GSM_MACBLOCK_LEN app_ccch_scan.c:397
backtrace() returned 20 addresses
/usr/local/lib/libosmocore.so.17(osmo_generate_backtrace+0x1e) [0xb7eedd3a]
/usr/local/lib/libosmocore.so.17(+0x1eb62) [0xb7eedb62]
/usr/local/lib/libosmocore.so.17(osmo_panic+0x48) [0xb7eedbaf]
./ccch_scan(+0x3976) [0x4f5976]
./ccch_scan(+0x3bf2) [0x4f5bf2]
./ccch_scan(+0x3ddb) [0x4f5ddb]
/usr/local/lib/libosmogsm.so.16(+0x2dbf1) [0xb7e7bbf1]
/usr/local/lib/libosmogsm.so.16(+0x2e03e) [0xb7e7c03e]
/usr/local/lib/libosmogsm.so.16(+0x2eed1) [0xb7e7ced1]
/usr/local/lib/libosmogsm.so.16(lapdm_phsap_up+0x118) [0xb7e7d143]
./ccch_scan(+0x57d4) [0x4f77d4]
./ccch_scan(+0x68ba) [0x4f88ba]
/usr/local/lib/libosmocore.so.17(osmo_wqueue_bfd_cb+0x36) [0xb7ee2b62]
/usr/local/lib/libosmocore.so.17(+0xc4bb) [0xb7edb4bb]
/usr/local/lib/libosmocore.so.17(+0xc589) [0xb7edb589]
/usr/local/lib/libosmocore.so.17(osmo_select_main+0x1d) [0xb7edb5b0]
./ccch_scan(+0x2a22) [0x4f4a22]
/lib/i386-linux-gnu/libc.so.6(__libc_start_main+0x106) [0xb7c61e46]
./ccch_scan(+0x2bc1) [0x4f4bc1]
zsh: abort sudo ./ccch_scan -i 127.0.0.1 -a 50