diff --git a/raygun4ruby.gemspec b/raygun4ruby.gemspec
index f36bfe6..651e78a 100644
--- a/raygun4ruby.gemspec
+++ b/raygun4ruby.gemspec
@@ -24,6 +24,7 @@ Gem::Specification.new do |spec|
   spec.add_runtime_dependency "json"
   spec.add_runtime_dependency "rack"
   spec.add_runtime_dependency "concurrent-ruby"
+  spec.add_runtime_dependency "ostruct"
 
   spec.add_development_dependency "bundler", ">= 2.3"
   spec.add_development_dependency "rake", ">= 12.3.3"