diff --git a/lib/rdoc/generator/darkfish.rb b/lib/rdoc/generator/darkfish.rb
index 60e0265e8c7c8b..7a7a95a9b95696 100644
--- a/lib/rdoc/generator/darkfish.rb
+++ b/lib/rdoc/generator/darkfish.rb
@@ -610,7 +610,7 @@ def setup
 
     @classes = @store.all_classes_and_modules.sort
     @files   = @store.all_files.sort
-    @methods = @classes.map { |m| m.method_list }.flatten.sort
+    @methods = @classes.flat_map { |m| m.method_list }.sort
     @modsort = get_sorted_module_list @classes
   end
 
diff --git a/lib/rdoc/generator/json_index.rb b/lib/rdoc/generator/json_index.rb
index 3a1000033df5a0..c454910d5c94f8 100644
--- a/lib/rdoc/generator/json_index.rb
+++ b/lib/rdoc/generator/json_index.rb
@@ -230,9 +230,9 @@ def index_classes
   def index_methods
     debug_msg "  generating method search index"
 
-    list = @classes.uniq.map do |klass|
+    list = @classes.uniq.flat_map do |klass|
       klass.method_list
-    end.flatten.sort_by do |method|
+    end.sort_by do |method|
       [method.name, method.parent.full_name]
     end
 
diff --git a/lib/rdoc/generator/template/darkfish/table_of_contents.rhtml b/lib/rdoc/generator/template/darkfish/table_of_contents.rhtml
index c8a422a521360f..54a376c9e55e05 100644
--- a/lib/rdoc/generator/template/darkfish/table_of_contents.rhtml
+++ b/lib/rdoc/generator/template/darkfish/table_of_contents.rhtml
@@ -47,9 +47,9 @@
 
 <h2 id="methods">Methods</h2>
 <ul>
-<%- @store.all_classes_and_modules.map do |mod|
+<%- @store.all_classes_and_modules.flat_map do |mod|
      mod.method_list
-   end.flatten.sort.each do |method| %>
+   end.sort.each do |method| %>
   <li class="method">
     <a href="<%= method.path %>"><%= h method.pretty_name %></a>
     &mdash;
diff --git a/lib/rdoc/markup/to_joined_paragraph.rb b/lib/rdoc/markup/to_joined_paragraph.rb
index aaa343157e8564..31cbe0853c6858 100644
--- a/lib/rdoc/markup/to_joined_paragraph.rb
+++ b/lib/rdoc/markup/to_joined_paragraph.rb
@@ -25,9 +25,9 @@ def end_accepting # :nodoc:
   def accept_paragraph paragraph
     parts = paragraph.parts.chunk do |part|
       String === part
-    end.map do |string, chunk|
+    end.flat_map do |string, chunk|
       string ? chunk.join.rstrip : chunk
-    end.flatten
+    end
 
     paragraph.parts.replace parts
   end
diff --git a/test/rdoc/test_rdoc_markup_to_html.rb b/test/rdoc/test_rdoc_markup_to_html.rb
index 935a7d70c5ec8a..6897c8132ef355 100644
--- a/test/rdoc/test_rdoc_markup_to_html.rb
+++ b/test/rdoc/test_rdoc_markup_to_html.rb
@@ -602,9 +602,9 @@ def test_accept_verbatim_ruby
   end
 
   def test_accept_verbatim_redefinable_operators
-    functions = %w[| ^ & <=> == === =~ > >= < <= << >> + - * / % ** ~ +@ -@ [] []= ` !  != !~].map { |redefinable_op|
+    functions = %w[| ^ & <=> == === =~ > >= < <= << >> + - * / % ** ~ +@ -@ [] []= ` !  != !~].flat_map { |redefinable_op|
       ["def #{redefinable_op}\n", "end\n"]
-    }.flatten
+    }
 
     verb = @RM::Verbatim.new(*functions)
 
diff --git a/test/rdoc/test_rdoc_store.rb b/test/rdoc/test_rdoc_store.rb
index 8350d257b38a01..50e8667d81b02f 100644
--- a/test/rdoc/test_rdoc_store.rb
+++ b/test/rdoc/test_rdoc_store.rb
@@ -373,9 +373,9 @@ def test_load_all
     assert_equal [@mod],                s.all_modules.sort
     assert_equal [@page, @top_level],   s.all_files.sort
 
-    methods = s.all_classes_and_modules.map do |mod|
+    methods = s.all_classes_and_modules.flat_map do |mod|
       mod.method_list
-    end.flatten.sort
+    end.sort
 
     _meth_bang_alias = RDoc::AnyMethod.new nil, 'method_bang'
     _meth_bang_alias.parent = @klass
@@ -388,9 +388,9 @@ def test_load_all
 
     assert_equal @klass, methods.last.parent
 
-    attributes = s.all_classes_and_modules.map do |mod|
+    attributes = s.all_classes_and_modules.flat_map do |mod|
       mod.attributes
-    end.flatten.sort
+    end.sort
 
     assert_equal [@attr], attributes