diff --git a/lib/rspec/openapi/schema_builder.rb b/lib/rspec/openapi/schema_builder.rb
index f99e4a5..dc9de21 100644
--- a/lib/rspec/openapi/schema_builder.rb
+++ b/lib/rspec/openapi/schema_builder.rb
@@ -47,7 +47,7 @@ def build(record)
   private
 
   def enrich_with_required_keys(obj)
-    obj[:required] = obj[:properties]&.keys
+    obj[:required] = obj[:properties]&.keys || []
     obj
   end
 
diff --git a/spec/rails/app/controllers/users_controller.rb b/spec/rails/app/controllers/users_controller.rb
index 8acafe6..2a66a2a 100644
--- a/spec/rails/app/controllers/users_controller.rb
+++ b/spec/rails/app/controllers/users_controller.rb
@@ -1,7 +1,7 @@
 class UsersController < ApplicationController
   def create
     res = {
-      name: params[:name],
+      name: params[:name] || 'alice',
       relations: {
         avatar: {
           url: params[:avatar_url] || 'https://example.com/avatar.png',
diff --git a/spec/rails/doc/smart/expected.yaml b/spec/rails/doc/smart/expected.yaml
index afa610e..99f795b 100644
--- a/spec/rails/doc/smart/expected.yaml
+++ b/spec/rails/doc/smart/expected.yaml
@@ -411,9 +411,5 @@ components:
               properties:
                 baz:
                   type: integer
-              required:
-                - baz
           required:
             - bar
-      required:
-        - name
diff --git a/spec/requests/rails_smart_merge_spec.rb b/spec/requests/rails_smart_merge_spec.rb
index 7afa0ab..42af1f2 100644
--- a/spec/requests/rails_smart_merge_spec.rb
+++ b/spec/requests/rails_smart_merge_spec.rb
@@ -82,6 +82,22 @@
       expect(response.status).to eq(201)
     end
 
+    it 'accepts nested object where some fields are missing' do
+      post '/users', headers: { authorization: 'k0kubun', 'Content-Type': 'application/json' }, params: {
+        name: 'alice',
+        foo: {
+          bar: {
+          },
+        },
+      }.to_json
+      expect(response.status).to eq(201)
+    end
+
+    it 'can accept empty body' do
+      post '/users', headers: { authorization: 'k0kubun', 'Content-Type': 'application/json' }, params: {}.to_json
+      expect(response.status).to eq(201)
+    end
+
     it 'returns an user' do
       post '/users', headers: { authorization: 'k0kubun', 'Content-Type': 'application/json' }, params: {
         name: 'alice',