diff --git a/koala.gemspec b/koala.gemspec
index 5c16e6f1..56058666 100644
--- a/koala.gemspec
+++ b/koala.gemspec
@@ -29,4 +29,5 @@ Gem::Specification.new do |gem|
   gem.add_runtime_dependency("json", ">= 1.8")
   gem.add_runtime_dependency("rexml")
   gem.add_runtime_dependency("base64")
+  gem.add_runtime_dependency("ostruct")
 end