diff --git a/activerecord/lib/active_record/model_schema.rb b/activerecord/lib/active_record/model_schema.rb
index 1971199a29..8ce155ff9f 100644
--- a/activerecord/lib/active_record/model_schema.rb
+++ b/activerecord/lib/active_record/model_schema.rb
@@ -213,6 +213,21 @@ module ActiveRecord
       # the table name guess for an Invoice class becomes "myapp_invoices".
       # Invoice::Lineitem becomes "myapp_invoice_lineitems".
       #
+      # Active Model Naming's +model_name+ is the base name used to guess the
+      # table name. In case a custom Active Model Name is defined, it will be
+      # used for the table name as well:
+      #
+      #   class PostRecord < ActiveRecord::Base
+      #     class << self
+      #       def model_name
+      #         ActiveModel::Name.new(self, nil, "Post")
+      #       end
+      #     end
+      #   end
+      #
+      #   PostRecord.table_name
+      #   # => "posts"
+      #
       # You can also set your own table name explicitly:
       #
       #   class Mouse < ActiveRecord::Base
@@ -587,8 +602,8 @@ module ActiveRecord
         end
 
         # Guesses the table name, but does not decorate it with prefix and suffix information.
-        def undecorated_table_name(class_name = base_class.name)
-          table_name = class_name.to_s.demodulize.underscore
+        def undecorated_table_name(model_name)
+          table_name = model_name.to_s.demodulize.underscore
           pluralize_table_names ? table_name.pluralize : table_name
         end
 
@@ -602,7 +617,7 @@ module ActiveRecord
               contained += "_"
             end
 
-            "#{full_table_name_prefix}#{contained}#{undecorated_table_name(name)}#{full_table_name_suffix}"
+            "#{full_table_name_prefix}#{contained}#{undecorated_table_name(model_name)}#{full_table_name_suffix}"
           else
             # STI subclasses always use their superclass' table.
             base_class.table_name
diff --git a/activerecord/test/cases/attribute_methods_test.rb b/activerecord/test/cases/attribute_methods_test.rb
index 0e20ceb3a1..6dead34126 100644
--- a/activerecord/test/cases/attribute_methods_test.rb
+++ b/activerecord/test/cases/attribute_methods_test.rb
@@ -965,6 +965,7 @@ class AttributeMethodsTest < ActiveRecord::TestCase
 
   test "define_attribute_method works with both symbol and string" do
     klass = Class.new(ActiveRecord::Base)
+    klass.table_name = "foo"
 
     assert_nothing_raised { klass.define_attribute_method(:foo) }
     assert_nothing_raised { klass.define_attribute_method("bar") }
diff --git a/activerecord/test/cases/base_test.rb b/activerecord/test/cases/base_test.rb
index 9968479bc8..5af09ed196 100644
--- a/activerecord/test/cases/base_test.rb
+++ b/activerecord/test/cases/base_test.rb
@@ -505,6 +505,10 @@ class BasicsTest < ActiveRecord::TestCase
     Post.reset_table_name
   end
 
+  def test_table_name_based_on_model_name
+    assert_equal "posts", PostRecord.table_name
+  end
+
   def test_null_fields
     assert_nil Topic.find(1).parent_id
     assert_nil Topic.create("title" => "Hey you").parent_id
@@ -1478,6 +1482,7 @@ class BasicsTest < ActiveRecord::TestCase
 
   test "scoped can take a values hash" do
     klass = Class.new(ActiveRecord::Base)
+    klass.table_name = "bar"
     assert_equal ["foo"], klass.all.merge!(select: "foo").select_values
   end
 
diff --git a/activerecord/test/cases/primary_keys_test.rb b/activerecord/test/cases/primary_keys_test.rb
index 1ee8842fc6..1707126f12 100644
--- a/activerecord/test/cases/primary_keys_test.rb
+++ b/activerecord/test/cases/primary_keys_test.rb
@@ -174,6 +174,7 @@ class PrimaryKeysTest < ActiveRecord::TestCase
 
   def test_quoted_primary_key_after_set_primary_key
     k = Class.new(ActiveRecord::Base)
+    k.table_name = "bar"
     assert_equal k.connection.quote_column_name("id"), k.quoted_primary_key
     k.primary_key = "foo"
     assert_equal k.connection.quote_column_name("foo"), k.quoted_primary_key
diff --git a/activerecord/test/models/post.rb b/activerecord/test/models/post.rb
index 74dd008efe..21a1674457 100644
--- a/activerecord/test/models/post.rb
+++ b/activerecord/test/models/post.rb
@@ -382,3 +382,11 @@ class Postesque < ActiveRecord::Base
   belongs_to :author_with_address, class_name: "Author", foreign_key: :author_id
   belongs_to :author_with_the_letter_a, class_name: "Author", foreign_key: :author_id
 end
+
+class PostRecord < ActiveRecord::Base
+  class << self
+    def model_name
+      ActiveModel::Name.new(self, nil, "Post")
+    end
+  end
+end
diff --git a/guides/source/active_support_core_extensions.md b/guides/source/active_support_core_extensions.md
index 5b43a378d6..a454733f2a 100644
--- a/guides/source/active_support_core_extensions.md
+++ b/guides/source/active_support_core_extensions.md
@@ -1461,8 +1461,8 @@ Active Record uses this method to compute the default table name that correspond
 
 ```ruby
 # active_record/model_schema.rb
-def undecorated_table_name(class_name = base_class.name)
-  table_name = class_name.to_s.demodulize.underscore
+def undecorated_table_name(model_name)
+  table_name = model_name.to_s.demodulize.underscore
   pluralize_table_names ? table_name.pluralize : table_name
 end
 ```