diff --git a/spree_avatax_certified.gemspec b/spree_avatax_certified.gemspec
index 2b253dd..56b6e61 100644
--- a/spree_avatax_certified.gemspec
+++ b/spree_avatax_certified.gemspec
@@ -36,10 +36,11 @@ Gem::Specification.new do |s|
   s.add_development_dependency 'selenium-webdriver'
   s.add_development_dependency 'simplecov'
   s.add_development_dependency 'sqlite3'
-  s.add_development_dependency 'mysql2'
+  s.add_development_dependency 'mysql2', '~> 0.3.18'
   s.add_development_dependency 'shoulda-matchers'
   s.add_development_dependency 'vcr'
   s.add_development_dependency 'webmock'
   s.add_development_dependency 'pg', '~> 0.18'
   s.add_development_dependency 'appraisal'
+  s.add_development_dependency 'puma'
 end