diff --git a/jsonapi-rails.gemspec b/jsonapi-rails.gemspec
index 48387d4..c89d3e2 100644
--- a/jsonapi-rails.gemspec
+++ b/jsonapi-rails.gemspec
@@ -16,6 +16,7 @@ Gem::Specification.new do |spec|
 
   spec.add_dependency 'jsonapi-rb', '~> 0.5.0'
   spec.add_dependency 'jsonapi-parser', '~> 0.1.0'
+  spec.add_dependency 'rack', '~> 2.0.7'
 
   spec.add_development_dependency 'rails', '~> 5.0'
   spec.add_development_dependency 'sqlite3', '~> 1.3.6'