ssl.cpp:333: error: ‘SSL_set_tlsext_host_name’ was not declared in this scope

[root@test ~]# gem install redis-stat
Building native extensions. This could take a while...
ERROR: Error installing redis-stat:
ERROR: Failed to build gem native extension.

current directory: /usr/local/lib/ruby/gems/2.3.0/gems/eventmachine-1.2.0.1/ext
/usr/local/bin/ruby -r ./siteconf20160702-16245-1884dow.rb extconf.rb
checking for main() in -lcrypto... yes
checking for main() in -lssl... yes
checking for openssl/ssl.h... yes
checking for openssl/err.h... yes
checking for rb_trap_immediate in ruby.h,rubysig.h... no
checking for rb_thread_blocking_region()... no
checking for rb_thread_call_without_gvl() in ruby/thread.h... yes
checking for rb_thread_fd_select()... yes
checking for rb_fdset_t in ruby/intern.h... yes
checking for rb_wait_for_single_fd()... yes
checking for rb_enable_interrupt()... no
checking for rb_time_new()... yes
checking for inotify_init() in sys/inotify.h... yes
checking for writev() in sys/uio.h... yes
checking for pipe2() in unistd.h... no
checking for accept4() in sys/socket.h... no
checking for SOCK_CLOEXEC in sys/socket.h... no
checking for sys/event.h... no
checking for epoll_create() in sys/epoll.h... yes
checking for clock_gettime()... yes
checking for CLOCK_MONOTONIC_RAW in time.h... no
checking for CLOCK_MONOTONIC in time.h... yes
CXXFLAGS=$(cxxflags) -Wall -Wextra -Wno-deprecated-declarations
creating Makefile

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

/usr/local/lib/ruby/gems/2.3.0/extensions/x86_64-linux/2.3.0-static/eventmachine-1.2.0.1/mkmf.log

current directory: /usr/local/lib/ruby/gems/2.3.0/gems/eventmachine-1.2.0.1/ext
make "DESTDIR=" clean

current directory: /usr/local/lib/ruby/gems/2.3.0/gems/eventmachine-1.2.0.1/ext
make "DESTDIR="
compiling kb.cpp
cc1plus: warning: command line option "-Wdeclaration-after-statement" is valid for C/ObjC but not for C++
cc1plus: warning: command line option "-Wimplicit-function-declaration" is valid for C/ObjC but not for C++
compiling rubymain.cpp
cc1plus: warning: command line option "-Wdeclaration-after-statement" is valid for C/ObjC but not for C++
cc1plus: warning: command line option "-Wimplicit-function-declaration" is valid for C/ObjC but not for C++
compiling ssl.cpp
cc1plus: warning: command line option "-Wdeclaration-after-statement" is valid for C/ObjC but not for C++
cc1plus: warning: command line option "-Wimplicit-function-declaration" is valid for C/ObjC but not for C++
ssl.cpp: In constructor ‘SslBox_t::SslBox_t(bool, const std::string&, const std::string&, bool, bool, const std::string&, const std::string&, const std::string&, const std::string&, int, uintptr_t)’:
ssl.cpp:333: error: ‘SSL_set_tlsext_host_name’ was not declared in this scope
make: *** [ssl.o] Error 1

make failed, exit code 2

Gem files will remain installed in /usr/local/lib/ruby/gems/2.3.0/gems/eventmachine-1.2.0.1 for inspection.
Results logged to /usr/local/lib/ruby/gems/2.3.0/extensions/x86_64-linux/2.3.0-static/eventmachine-1.2.0.1/gem_make.out
[root@test ~]#