diff --git a/trmnl-api.gemspec b/trmnl-api.gemspec
index e614646..fa0a807 100644
--- a/trmnl-api.gemspec
+++ b/trmnl-api.gemspec
@@ -27,6 +27,7 @@ Gem::Specification.new do |spec|
   spec.add_dependency "containable", "~> 1.2"
   spec.add_dependency "dry-monads", "~> 1.8"
   spec.add_dependency "dry-schema", "~> 1.14"
+  spec.add_dependency "dry-types", "~> 1.8"
   spec.add_dependency "http", "~> 5.3"
   spec.add_dependency "infusible", "~> 4.3"
   spec.add_dependency "inspectable", "~> 0.3"