diff --git a/samples/client/petstore/ruby-faraday/spec/api_client_spec.rb b/samples/client/petstore/ruby-faraday/spec/api_client_spec.rb
index 0f41c29b81b..723812b87f1 100644
--- a/samples/client/petstore/ruby-faraday/spec/api_client_spec.rb
+++ b/samples/client/petstore/ruby-faraday/spec/api_client_spec.rb
@@ -159,8 +159,8 @@ describe Petstore::ApiClient do
     let(:api_client) { Petstore::ApiClient.new }
 
     it 'works' do
-      expect(api_client.select_header_content_type(nil)).to eq('application/json')
-      expect(api_client.select_header_content_type([])).to eq('application/json')
+      expect(api_client.select_header_content_type(nil)).to be_nil
+      expect(api_client.select_header_content_type([])).to be_nil
 
       expect(api_client.select_header_content_type(['application/json'])).to eq('application/json')
       expect(api_client.select_header_content_type(['application/xml', 'application/json; charset=UTF8'])).to eq('application/json; charset=UTF8')
diff --git a/samples/client/petstore/ruby/spec/api_client_spec.rb b/samples/client/petstore/ruby/spec/api_client_spec.rb
index b91cd25d81f..1355cb28d68 100644
--- a/samples/client/petstore/ruby/spec/api_client_spec.rb
+++ b/samples/client/petstore/ruby/spec/api_client_spec.rb
@@ -197,8 +197,8 @@ describe Petstore::ApiClient do
     let(:api_client) { Petstore::ApiClient.new }
 
     it 'works' do
-      expect(api_client.select_header_content_type(nil)).to eq('application/json')
-      expect(api_client.select_header_content_type([])).to eq('application/json')
+      expect(api_client.select_header_content_type(nil)).to be_nil
+      expect(api_client.select_header_content_type([])).to be_nil
 
       expect(api_client.select_header_content_type(['application/json'])).to eq('application/json')
       expect(api_client.select_header_content_type(['application/xml', 'application/json; charset=UTF8'])).to eq('application/json; charset=UTF8')