memcached server incr/decr doesn't work in unsigned 64bit integer mode

[mlinhard@michal-linhard ~]$ telnet localhost 11211
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
set a 0 0 19
9223372036854775808
STORED
incr a 1
SERVER_ERROR org.infinispan.server.core.ServerException: java.lang.NumberFormatException: For input string: "9223372036854775808"

when I run original memcached server on port 11212 it works:
[mlinhard@michal-linhard ~]$ telnet localhost 11212
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
set a 0 0 1
A
STORED
set a 0 0 19
9223372036854775808
STORED
incr a 1
9223372036854775809

----------------
Other issue here is overflow:
set a 0 0 19
9223372036854775807
incr a 1
-9223372036854775808

whereas original memcached server overflows in "unsigned mode":
set b 0 0 20
18446744073709551615
incr b 1
0