diff --git a/doorkeeper-openid_connect.gemspec b/doorkeeper-openid_connect.gemspec
index b4900f1..92ebac3 100644
--- a/doorkeeper-openid_connect.gemspec
+++ b/doorkeeper-openid_connect.gemspec
@@ -25,6 +25,7 @@ Gem::Specification.new do |spec|
   spec.required_ruby_version = '>= 3.1'
 
   spec.add_runtime_dependency 'doorkeeper', '>= 5.5', '< 5.9'
+  spec.add_runtime_dependency 'ostruct', '>= 0.5'
   spec.add_runtime_dependency 'jwt', '>= 2.5'
 
   spec.add_development_dependency 'bigdecimal'