diff --git a/spec/helpers.rb b/spec/helpers.rb
index b8252d0da..992f53265 100644
--- a/spec/helpers.rb
+++ b/spec/helpers.rb
@@ -474,7 +474,7 @@ def create_cert_from_csr(name, csr, ca_cert, ca_key, valid_years: 10, dns_names:
 
 			csr_cert.sign ca_key, OpenSSL::Digest::SHA256.new
 
-			open "#{output_dir}/#{name}", 'w' do |io|
+			File.open "#{output_dir}/#{name}", 'w' do |io|
 				io.puts csr_cert.to_text
 				io.write csr_cert.to_pem
 			end