diff --git a/lib/org-ruby/output_buffer.rb b/lib/org-ruby/output_buffer.rb
index 90a0aae..3179cd5 100644
--- a/lib/org-ruby/output_buffer.rb
+++ b/lib/org-ruby/output_buffer.rb
@@ -137,7 +137,7 @@ def preserve_whitespace?
     end
 
     def do_custom_markup
-      if File.exists? @options[:markup_file]
+      if File.exist? @options[:markup_file]
         load_custom_markup
         if @custom_blocktags.empty?
           no_valid_markup_found
diff --git a/lib/org-ruby/parser.rb b/lib/org-ruby/parser.rb
index a57fd9e..192b855 100644
--- a/lib/org-ruby/parser.rb
+++ b/lib/org-ruby/parser.rb
@@ -129,7 +129,7 @@ def initialize(lines, parser_options={ })
 
     # Check include file availability and permissions
     def check_include_file(file_path)
-      can_be_included = File.exists? file_path
+      can_be_included = File.exist? file_path
 
       if not ENV['ORG_RUBY_INCLUDE_ROOT'].nil?
         # Ensure we have full paths