diff --git a/activesupport/lib/active_support/hash_with_indifferent_access.rb b/activesupport/lib/active_support/hash_with_indifferent_access.rb
index 1402c510e9..2f771d7e97 100644
--- a/activesupport/lib/active_support/hash_with_indifferent_access.rb
+++ b/activesupport/lib/active_support/hash_with_indifferent_access.rb
@@ -378,13 +378,10 @@ def compact
 
     # Convert to a regular hash with string keys.
     def to_hash
-      _new_hash = Hash.new
-      set_defaults(_new_hash)
-
-      each do |key, value|
-        _new_hash[key] = convert_value(value, conversion: :to_hash)
-      end
-      _new_hash
+      copy = Hash[self]
+      copy.transform_values! { |v| convert_value_to_hash(v) }
+      set_defaults(copy)
+      copy
     end
 
     def to_proc
@@ -398,11 +395,7 @@ def convert_key(key)
 
       def convert_value(value, conversion: nil)
         if value.is_a? Hash
-          if conversion == :to_hash
-            value.to_hash
-          else
-            value.nested_under_indifferent_access
-          end
+          value.nested_under_indifferent_access
         elsif value.is_a?(Array)
           if conversion != :assignment || value.frozen?
             value = value.dup
@@ -413,6 +406,17 @@ def convert_value(value, conversion: nil)
         end
       end
 
+      def convert_value_to_hash(value)
+        if value.is_a? Hash
+          value.to_hash
+        elsif value.is_a?(Array)
+          value.map { |e| convert_value_to_hash(e) }
+        else
+          value
+        end
+      end
+
+
       def set_defaults(target)
         if default_proc
           target.default_proc = default_proc.dup