diff --git a/active_flag.gemspec b/active_flag.gemspec
index b7e2380..fcdaedf 100644
--- a/active_flag.gemspec
+++ b/active_flag.gemspec
@@ -22,6 +22,7 @@ Gem::Specification.new do |spec|
   spec.add_runtime_dependency 'activerecord', '>= 5'
   spec.add_runtime_dependency 'logger'
   spec.add_runtime_dependency 'mutex_m'
+  spec.add_runtime_dependency 'bigdecimal'
   spec.add_development_dependency 'bundler'
   spec.add_development_dependency 'rake'
   spec.add_development_dependency 'minitest'