diff --git a/lib/active_interaction/backports.rb b/lib/active_interaction/backports.rb
index 0793a584..56b6e391 100644
--- a/lib/active_interaction/backports.rb
+++ b/lib/active_interaction/backports.rb
@@ -19,15 +19,3 @@ class Errors
     protected :initialize_dup
   end
 end
-
-# @private
-class Hash
-  # Required for Rails < 4.0.0.
-  def transform_keys
-    result = {}
-    each_key do |key|
-      result[yield(key)] = self[key]
-    end
-    result
-  end unless method_defined?(:transform_keys)
-end
diff --git a/lib/active_interaction/filters/hash_filter.rb b/lib/active_interaction/filters/hash_filter.rb
index b3135ddb..94249468 100644
--- a/lib/active_interaction/filters/hash_filter.rb
+++ b/lib/active_interaction/filters/hash_filter.rb
@@ -32,11 +32,12 @@ class HashFilter < Filter
     def cast(value)
       case value
       when Hash
-        value = stringify_the_symbol_keys(value)
+        value = value.with_indifferent_access
+        initial = strip? ? ActiveSupport::HashWithIndifferentAccess.new : value
 
-        filters.each_with_object(strip? ? {} : value) do |(name, filter), h|
+        filters.each_with_object(initial) do |(name, filter), h|
           clean_value(h, name.to_s, filter, value)
-        end.symbolize_keys
+        end
       else
         super
       end
@@ -74,9 +75,5 @@ def raw_default
     def strip?
       options.fetch(:strip, true)
     end
-
-    def stringify_the_symbol_keys(hash)
-      hash.transform_keys { |key| key.is_a?(Symbol) ? key.to_s : key }
-    end
   end
 end
diff --git a/spec/active_interaction/filters/hash_filter_spec.rb b/spec/active_interaction/filters/hash_filter_spec.rb
index 492896e5..b5778120 100644
--- a/spec/active_interaction/filters/hash_filter_spec.rb
+++ b/spec/active_interaction/filters/hash_filter_spec.rb
@@ -37,7 +37,7 @@
       let(:block) { proc { hash :a } }
 
       context 'with a Hash' do
-        let(:value) { { a: {} } }
+        let(:value) { { 'a' => {} } }
 
         it 'returns the Hash' do
           expect(result).to eql value
diff --git a/spec/active_interaction/integration/hash_interaction_spec.rb b/spec/active_interaction/integration/hash_interaction_spec.rb
index 988b070d..29561fed 100644
--- a/spec/active_interaction/integration/hash_interaction_spec.rb
+++ b/spec/active_interaction/integration/hash_interaction_spec.rb
@@ -21,11 +21,11 @@
     before { inputs.merge!(a: a) }
 
     it 'returns the correct value for :a' do
-      expect(result[:a]).to eql a.symbolize_keys
+      expect(result[:a]).to eql a.with_indifferent_access
     end
 
     it 'returns the correct value for :b' do
-      expect(result[:b]).to eql(x: {})
+      expect(result[:b]).to eql('x' => {})
     end
   end