Update to RubyInstaller2-2.4.1-1rc1 which moved the add_dll_directory function.

lib/fox16.rb

@@ -8,8 +8,8 @@ rescue LoadError
 
     add_dll_path = proc do |path, &block|
       begin
-        require 'ruby_installer'
-        RubyInstaller.add_dll_directory(path, &block)
+        require 'ruby_installer/runtime'
+        RubyInstaller::Runtime.add_dll_directory(path, &block)
       rescue LoadError
         old_path = ENV['PATH']
         ENV['PATH'] = "#{path};#{old_path}"