diff --git a/activesupport/lib/active_support/hash_with_indifferent_access.rb b/activesupport/lib/active_support/hash_with_indifferent_access.rb
index 1927cddf34fa2caef8a4a470565706cb6b7df8db..8b34b8b28b87a025193b06c4816170a99c3eaad2 100644
--- a/activesupport/lib/active_support/hash_with_indifferent_access.rb
+++ b/activesupport/lib/active_support/hash_with_indifferent_access.rb
@@ -74,16 +74,6 @@ def initialize(constructor = {})
       end
     end
 
-    def default(*args)
-      arg_key = args.first
-
-      if include?(key = convert_key(arg_key))
-        self[key]
-      else
-        super
-      end
-    end
-
     def self.[](*args)
       new.merge!(Hash[*args])
     end
@@ -185,6 +175,36 @@ def fetch(key, *extras)
       super(convert_key(key), *extras)
     end
 
+    if Hash.new.respond_to?(:dig)
+      # Same as <tt>Hash#dig</tt> where the key passed as argument can be
+      # either a string or a symbol:
+      #
+      #   counters = ActiveSupport::HashWithIndifferentAccess.new
+      #   counters[:foo] = { bar: 1 }
+      #
+      #   counters.dig('foo', 'bar')     # => 1
+      #   counters.dig(:foo, :bar)       # => 1
+      #   counters.dig(:zoo)             # => nil
+      def dig(*args)
+        args[0] = convert_key(args[0]) if args.size > 0
+        super(*args)
+      end
+    end
+
+    # Same as <tt>Hash#default</tt> where the key passed as argument can be
+    # either a string or a symbol:
+    #
+    #   hash = ActiveSupport::HashWithIndifferentAccess.new(1)
+    #   hash.default                   # => 1
+    #
+    #   hash = ActiveSupport::HashWithIndifferentAccess.new { |hash, key| key }
+    #   hash.default                   # => nil
+    #   hash.default('foo')            # => 'foo'
+    #   hash.default(:foo)             # => 'foo'
+    def default(*args)
+      super(*args.map { |arg| convert_key(arg) })
+    end
+
     # Returns an array of the values at the specified indices:
     #
     #   hash = ActiveSupport::HashWithIndifferentAccess.new
diff --git a/activesupport/test/core_ext/hash_ext_test.rb b/activesupport/test/core_ext/hash_ext_test.rb
index 525ea08abd08c7df366f728dad21330f7b3a2185..7777d0b1bc2688fd302f9fbd68db196e4ff93ec2 100644
--- a/activesupport/test/core_ext/hash_ext_test.rb
+++ b/activesupport/test/core_ext/hash_ext_test.rb
@@ -729,6 +729,32 @@ def test_nested_dig_indifferent_access
     assert_equal 1234, data.dig(:this, :views)
   end
 
+  def test_argless_default_with_existing_nil_key
+    h = Hash.new(:default).merge(nil => "defined").with_indifferent_access
+
+    assert_equal :default, h.default
+  end
+
+  def test_default_with_argument
+    h = Hash.new { 5 }.merge(1 => 2).with_indifferent_access
+
+    assert_equal 5, h.default(1)
+  end
+
+  def test_default_proc
+    h = ActiveSupport::HashWithIndifferentAccess.new { |hash, key| key }
+
+    assert_nil h.default
+    assert_equal "foo", h.default("foo")
+    assert_equal "foo", h.default(:foo)
+  end
+
+  def test_double_conversion_with_nil_key
+    h = { nil => "defined" }.with_indifferent_access.with_indifferent_access
+
+    assert_equal nil, h[:undefined_key]
+  end
+
   def test_assert_valid_keys
     assert_nothing_raised do
       { failure: "stuff", funny: "business" }.assert_valid_keys([ :failure, :funny ])