Failure when installing gem using the embedded ruby v 2.5.1p57

[adamthedeveloper]

$ sudo /opt/td-agent/embedded/bin/gem install fluent-plugin-http-puma
Building native extensions.  This could take a while...
ERROR:  Error installing fluent-plugin-http-puma:
	ERROR: Failed to build gem native extension.

    current directory: /opt/td-agent/embedded/lib/ruby/gems/2.5.0/gems/msgpack-0.5.12/ext/msgpack
/opt/td-agent/embedded/bin/ruby -r ./siteconf20180713-20142-1s6zn9a.rb extconf.rb
checking for ruby/st.h... yes
checking for st.h... yes
checking for rb_str_replace() in ruby.h... yes
checking for rb_intern_str() in ruby.h... yes
checking for rb_sym2str() in ruby.h... yes
checking for rb_str_intern() in ruby.h... yes
creating Makefile

current directory: /opt/td-agent/embedded/lib/ruby/gems/2.5.0/gems/msgpack-0.5.12/ext/msgpack
make "DESTDIR=" clean

current directory: /opt/td-agent/embedded/lib/ruby/gems/2.5.0/gems/msgpack-0.5.12/ext/msgpack
make "DESTDIR="
compiling buffer.c
compiling buffer_class.c
compiling core_ext.c
core_ext.c: In function ‘MessagePack_core_ext_module_init’:
core_ext.c:121:22: error: ‘rb_cFixnum’ undeclared (first use in this function)
     rb_define_method(rb_cFixnum, "to_msgpack", Fixnum_to_msgpack, -1);
                      ^
core_ext.c:121:22: note: each undeclared identifier is reported only once for each function it appears in
core_ext.c:122:22: error: ‘rb_cBignum’ undeclared (first use in this function)
     rb_define_method(rb_cBignum, "to_msgpack", Bignum_to_msgpack, -1);
                      ^
Makefile:241: recipe for target 'core_ext.o' failed
make: *** [core_ext.o] Error 1

make failed, exit code 2

I was able to work around this temporarily by setting a different ruby (#!/usr/local/bin/ruby) at the top of the /opt/td-agent/embedded/bin/gem file. My ruby -v is ruby 2.3.5p376 (2017-09-14 revision 59905) [x86_64-linux]

Let me know if I can be more helpful.