diff --git a/lib/sidekiq_unique_jobs/core_ext.rb b/lib/sidekiq_unique_jobs/core_ext.rb
index ca0e3d6e..3ecc171d 100644
--- a/lib/sidekiq_unique_jobs/core_ext.rb
+++ b/lib/sidekiq_unique_jobs/core_ext.rb
@@ -98,7 +98,7 @@ def slice!(*keys)
     def _deep_transform_keys_in_object(object, &block)
       case object
       when Hash
-        object.each_with_object({}) do |(key, value), result|
+        object.each_with_object(self.class.new) do |(key, value), result|
           result[yield(key)] = _deep_transform_keys_in_object(value, &block)
         end
       when Array
diff --git a/spec/sidekiq_unique_jobs/core_ext_spec.rb b/spec/sidekiq_unique_jobs/core_ext_spec.rb
index 6d29bc09..8964ee8e 100644
--- a/spec/sidekiq_unique_jobs/core_ext_spec.rb
+++ b/spec/sidekiq_unique_jobs/core_ext_spec.rb
@@ -25,6 +25,20 @@
     end
   end
 
+  describe "ExtendedHash" do
+    before do
+      stub_const("ExtendedHash", Hash)
+    end
+
+    let(:hash) { ExtendedHash[:test, :me, :not, :me] }
+
+    describe "#deep_transform_keys" do
+      subject(:deep_transform_keys) { hash.deep_transform_keys(&:to_s) }
+
+      it { is_expected.to be_a(ExtendedHash) }
+    end
+  end
+
   describe Array do
     let(:array)         { [1, 2, nil, last_argument] }
     let(:last_argument) { Object.new }