won't build on ruby 2.3.0

[tibers]

[root@somehow]# rvm list

rvm rubies

   jruby-9.0.0.0 [ x86_64 ]
   jruby-9.1.2.0 [ x86_64 ]
   ruby-1.9.3-p551 [ x86_64 ]
   ruby-2.2.2 [ x86_64 ]
=* ruby-2.3.0 [ x86_64 ]

# => - current
# =* - current && default
#  * - default

[root@somehow]# gem install krypt
Building native extensions.  This could take a while...
ERROR:  Error installing krypt:
    ERROR: Failed to build gem native extension.

    current directory: /usr/local/rvm/gems/ruby-2.3.0/gems/krypt-core-0.0.2/ext/krypt/core
/usr/local/rvm/rubies/ruby-2.3.0/bin/ruby -r ./siteconf20160929-11362-aev2xx.rb extconf.rb
=== krypt-core API - C version ===
=== Checking Ruby features ===
checking for ruby/io.h... yes
checking for rb_big_pack()... yes
checking for rb_enumeratorize()... yes
checking for rb_str_encode()... yes
=== Checking platform features ===
checking for gmtime_r()... yes
creating extconf.h
creating Makefile
Done.

To see why this extension failed to compile, please check the mkmf.log which can be found here:

  /usr/local/rvm/gems/ruby-2.3.0/extensions/x86_64-linux/2.3.0/krypt-core-0.0.2/mkmf.log

current directory: /usr/local/rvm/gems/ruby-2.3.0/gems/krypt-core-0.0.2/ext/krypt/core
make "DESTDIR=" clean

current directory: /usr/local/rvm/gems/ruby-2.3.0/gems/krypt-core-0.0.2/ext/krypt/core
make "DESTDIR="
compiling krypt_asn1_parser.c
compiling krypt_asn1-internal.c
compiling krypt_io_in_pem.c
compiling krypt_io.c
compiling krypt_asn1.c
compiling krypt-core.c
compiling krypt_asn1_template_parser.c
compiling krypt_missing.c
krypt_missing.c: In function ‘krypt_asn1_encode_bignum’:
krypt_missing.c:66:5: warning: implicit declaration of function ‘RBIGNUM_LEN’ [-Wimplicit-function-declaration]
     biglen = RBIGNUM_LEN(bignum);
     ^
krypt_missing.c:67:29: error: ‘SIZEOF_BDIGITS’ undeclared (first use in this function)
     divisor = SIZEOF_LONG / SIZEOF_BDIGITS;
                             ^
krypt_missing.c:67:29: note: each undeclared identifier is reported only once for each function it appears in
krypt_missing.c: In function ‘krypt_asn1_decode_bignum’:
krypt_missing.c:189:2: warning: implicit declaration of function ‘RBIGNUM_SET_SIGN’ [-Wimplicit-function-declaration]
  RBIGNUM_SET_SIGN(value, !sign);
  ^
make: *** [krypt_missing.o] Error 1

make failed, exit code 2

Gem files will remain installed in /usr/local/rvm/gems/ruby-2.3.0/gems/krypt-core-0.0.2 for inspection.
Results logged to /usr/local/rvm/gems/ruby-2.3.0/extensions/x86_64-linux/2.3.0/krypt-core-0.0.2/gem_make.out
[root@somehow]#