diff --git a/lib/rdoc/markup/to_bs.rb b/lib/rdoc/markup/to_bs.rb
index d55f64c5e7..9a1c7c6ccd 100644
--- a/lib/rdoc/markup/to_bs.rb
+++ b/lib/rdoc/markup/to_bs.rb
@@ -64,7 +64,6 @@ def convert_special special
   # Adds bold or underline mixed with backspaces
 
   def convert_string string
-    return string unless string.respond_to? :chars # your ruby is lame
     return string unless @in_b or @in_em
     chars = if @in_b then
               string.chars.map do |char| "#{char}\b#{char}" end
@@ -76,4 +75,3 @@ def convert_string string
   end
 
 end
-
diff --git a/lib/rdoc/parser.rb b/lib/rdoc/parser.rb
index 9c207edcff..5abc374bf7 100644
--- a/lib/rdoc/parser.rb
+++ b/lib/rdoc/parser.rb
@@ -76,25 +76,15 @@ def self.binary?(file)
 
     s = File.read(file, 1024) or return false
 
-    have_encoding = s.respond_to? :encoding
-
     return true if s[0, 2] == Marshal.dump('')[0, 2] or s.index("\x00")
 
-    if have_encoding then
-      mode = "r"
-      s.sub!(/\A#!.*\n/, '')     # assume shebang line isn't longer than 1024.
-      encoding = s[/^\s*\#\s*(?:-\*-\s*)?(?:en)?coding:\s*([^\s;]+?)(?:-\*-|[\s;])/, 1]
-      mode = "rb:#{encoding}" if encoding
-      s = File.open(file, mode) {|f| f.gets(nil, 1024)}
-
-      not s.valid_encoding?
-    else
-      if 0.respond_to? :fdiv then
-        s.count("\x00-\x7F", "^ -~\t\r\n").fdiv(s.size) > 0.3
-      else # HACK 1.8.6
-        (s.count("\x00-\x7F", "^ -~\t\r\n").to_f / s.size) > 0.3
-      end
-    end
+    mode = "r"
+    s.sub!(/\A#!.*\n/, '')     # assume shebang line isn't longer than 1024.
+    encoding = s[/^\s*\#\s*(?:-\*-\s*)?(?:en)?coding:\s*([^\s;]+?)(?:-\*-|[\s;])/, 1]
+    mode = "rb:#{encoding}" if encoding
+    s = File.open(file, mode) {|f| f.gets(nil, 1024)}
+
+    not s.valid_encoding?
   end
 
   ##
@@ -308,4 +298,3 @@ def initialize top_level, file_name, content, options, stats
 require 'rdoc/parser/markdown'
 require 'rdoc/parser/rd'
 require 'rdoc/parser/ruby'
-
diff --git a/lib/rdoc/rdoc.rb b/lib/rdoc/rdoc.rb
index ec50d8eba5..20ec2414e6 100644
--- a/lib/rdoc/rdoc.rb
+++ b/lib/rdoc/rdoc.rb
@@ -479,7 +479,7 @@ def document options
       @last_modified = setup_output_dir @options.op_dir, @options.force_update
     end
 
-    @store.encoding = @options.encoding if @options.respond_to? :encoding
+    @store.encoding = @options.encoding
     @store.dry_run  = @options.dry_run
     @store.main     = @options.main_page
     @store.title    = @options.title
diff --git a/lib/rdoc/rubygems_hook.rb b/lib/rdoc/rubygems_hook.rb
index e2afb1fa91..f3840f327e 100644
--- a/lib/rdoc/rubygems_hook.rb
+++ b/lib/rdoc/rubygems_hook.rb
@@ -183,7 +183,7 @@ def generate
     @rdoc.options = options
 
     store = RDoc::Store.new
-    store.encoding = options.encoding if options.respond_to? :encoding
+    store.encoding = options.encoding
     store.dry_run  = options.dry_run
     store.main     = options.main_page
     store.title    = options.title
diff --git a/lib/rdoc/stats/normal.rb b/lib/rdoc/stats/normal.rb
index f32db48005..ba00b6cbdf 100644
--- a/lib/rdoc/stats/normal.rb
+++ b/lib/rdoc/stats/normal.rb
@@ -1,8 +1,5 @@
 # frozen_string_literal: false
-begin
-  require 'io/console/size'
-rescue LoadError
-end
+require 'io/console/size'
 
 ##
 # Stats printer that prints just the files being documented with a progress
@@ -26,11 +23,7 @@ def print_file files_so_far, filename
 
     # Print a progress bar, but make sure it fits on a single line. Filename
     # will be truncated if necessary.
-    terminal_width = if defined?(IO) && IO.respond_to?(:console_size)
-                       IO.console_size[1].to_i.nonzero? || 80
-                     else
-                       80
-                     end
+    terminal_width = IO.console_size[1].to_i.nonzero? || 80
     max_filename_size = terminal_width - progress_bar.size
 
     if filename.size > max_filename_size then
@@ -57,4 +50,3 @@ def done_adding # :nodoc:
   end
 
 end
-
diff --git a/lib/rdoc/store.rb b/lib/rdoc/store.rb
index 37bf03fc24..aaefff8f13 100644
--- a/lib/rdoc/store.rb
+++ b/lib/rdoc/store.rb
@@ -679,12 +679,7 @@ def method_file klass_name, method_name
     method_name =~ /#(.*)/
     method_type = $1 ? 'i' : 'c'
     method_name = $1 if $1
-
-    method_name = if ''.respond_to? :ord then
-                    method_name.gsub(/\W/) { "%%%02x" % $&[0].ord }
-                  else
-                    method_name.gsub(/\W/) { "%%%02x" % $&[0] }
-                  end
+    method_name = method_name.gsub(/\W/) { "%%%02x" % $&[0].ord }
 
     File.join class_path(klass_name), "#{method_name}-#{method_type}.ri"
   end
diff --git a/test/test_rdoc_parser.rb b/test/test_rdoc_parser.rb
index 732beb6629..b71d89b064 100644
--- a/test/test_rdoc_parser.rb
+++ b/test/test_rdoc_parser.rb
@@ -119,7 +119,7 @@ def test_class_for_forbidden
       end
       io
     end
-    tf.close! if tf.respond_to? :close!
+    tf.close!
   end
 
   def test_class_for_modeline
diff --git a/test/test_rdoc_rd_block_parser.rb b/test/test_rdoc_rd_block_parser.rb
index 7afa9a03dd..18ec30db0f 100644
--- a/test/test_rdoc_rd_block_parser.rb
+++ b/test/test_rdoc_rd_block_parser.rb
@@ -165,7 +165,7 @@ def test_parse_include_subtree
       assert_equal expected, parse(str)
       io
     end
-    tf.close! if tf.respond_to? :close!
+    tf.close!
   end
 
   def test_parse_heading
diff --git a/test/test_rdoc_rdoc.rb b/test/test_rdoc_rdoc.rb
index 55096d394e..0a5ff1c841 100644
--- a/test/test_rdoc_rdoc.rb
+++ b/test/test_rdoc_rdoc.rb
@@ -261,7 +261,7 @@ def test_parse_file_encoding
       assert_equal Encoding::ISO_8859_1, top_level.absolute_name.encoding
       io
     end
-    tf.close! if tf.respond_to? :close!
+    tf.close!
   end
 
   def test_parse_file_forbidden
@@ -290,7 +290,7 @@ def test_parse_file_forbidden
       end
       io
     end
-    tf.close! if tf.respond_to? :close!
+    tf.close!
   end
 
   def test_remove_unparseable
@@ -398,7 +398,7 @@ def test_setup_output_dir_exists_file
                    e.message)
       tempfile
     end
-    tf.close! if tf.respond_to? :close!
+    tf.close!
   end
 
   def test_setup_output_dir_exists_not_rdoc