Problem add plruby to PostgreSQL 9.5 on Centos 6

[HBrener]

Installing on Centos 6 PostgreSQL 9.5 (64 bit) ; ruby 1.8 and get from plruby libraries.
Trying add plruby to PostgreSQL -
create function plruby_call_handler() returns language_handler
as '/usr/lib64/ruby/site_ruby/1.8/x86_64-linux/plruby.so'
language 'c';
The follows error appears - could not load library "/usr/lib64/ruby/site_ruby/1.8/x86_64-linux/plruby.so": /usr/lib64/ruby/site_ruby/1.8/x86_64-linux/plruby.so: undefined symbol: FunctionCall3

What could be a problem!?
Thanks in advance Hanan Brener

[HBrener]

Additional information -
the plruby library we get from https://pkgs.org/centos-6/epel-x86_64/postgresql-plruby-0.5.3-4.el6.x86_64.rpm.html. Install this rpm required installation of postgresql95-libs-9.5.2-1PGDG.rhel6.x86_64