ep-engine crash in ep-engine.cc:920 and bucke-engine:1023

Thread 1 (process 20792):
#0 0x0000003d94e30265 in raise () from /lib64/libc.so.6
#1 0x0000003d94e31d10 in abort () from /lib64/libc.so.6
#2 0x00002aaaaad2b219 in EventuallyPersistentEngine (this=0x1372b070,
get_server_api=0x2aaaaaaac700 <bucket_get_server_api>) at atomic.hh:39
#3 0x00002aaaaad2b640 in create_instance (interface=<value optimized out>,
get_server_api=0x2aaaaaaac700 <bucket_get_server_api>, handle=0x42d86b98)
at ep_engine.cc:920
#4 0x00002aaaaaaacd66 in load_engine (dlhandle=0x13793538,
soname=0x42d87040 "/opt/membase/lib/memcached/ep.so")
at bucket_engine.c:1023
#5 0x00002aaaaaaaed96 in create_bucket (e=0x2aaaaacb3400,
bucket_name=0x42d871c0 "default",
path=0x42d87040 "/opt/membase/lib/memcached/ep.so",
config=0x42d87061 "ht_size=3079;ht_locks=5;db_shards=4;tap_noop_interval=20;max_txn_size=1000;max_size=1646264320;initfile=/opt/membase/etc/membase/init.sql;tap_keepalive=300;dbname=/opt/membase/var/lib/membase/data/def"...,
e_out=0x0, msg=0x42d86c30 "", msglen=1024) at bucket_engine.c:765
#6 0x00002aaaaaaaf24e in handle_create_bucket (handle=0x2aaaaacb3400,
cookie=0x136f16c8, request=<value optimized out>,
response=0x404b20 <binary_response_handler>) at bucket_engine.c:2112
#7 0x00002aaaaaab0393 in bucket_unknown_command (handle=0x2aaaaacb3400,
cookie=0x136f16c8, request=0x137170c0,
response=0x404b20 <binary_response_handler>) at bucket_engine.c:2374
#8 0x0000000000406a06 in process_bin_packet (c=0x136f16c8)
at daemon/memcached.c:2593
#9 0x0000000000410af5 in complete_nread_binary (c=0x5135)
at daemon/memcached.c:3389
#10 0x0000000000411791 in conn_nread (c=0x136f16c8) at daemon/memcached.c:3471
#11 0x00000000004073f4 in event_handler (fd=<value optimized out>,
which=<value optimized out>, arg=0x136f16c8) at daemon/memcached.c:5576
#12 0x00002b75859cddf9 in event_base_loop (base=0x13675120, flags=0)
at event.c:1308
#13 0x0000000000413394 in worker_libevent (arg=0x13674bc0)
at daemon/thread.c:304
#14 0x0000003d95a064a7 in start_thread () from /lib64/libpthread.so.0
#15 0x0000003d94ed3c2d in clone () from /lib64/libc.so.6