diff --git a/down.gemspec b/down.gemspec
index 231f08c..e72f3c9 100644
--- a/down.gemspec
+++ b/down.gemspec
@@ -23,4 +23,5 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency "httpx", "~> 0", "< 2.0.0"
   spec.add_development_dependency "http", RUBY_VERSION >= "2.5" ? "~> 5.0" : "~> 4.3"
   spec.add_development_dependency "warning" if RUBY_VERSION >= "2.4"
+  spec.add_development_dependency "csv"
 end