diff --git a/ice_nine.gemspec b/ice_nine.gemspec
index fcb0c57..9ff1efe 100644
--- a/ice_nine.gemspec
+++ b/ice_nine.gemspec
@@ -21,4 +21,5 @@ Gem::Specification.new do |gem|
 
   gem.add_development_dependency('bundler', '~> 2.2',  '>= 2.2.33')
   gem.add_development_dependency('rake',    '~> 13.0', '>= 13.0.6')
+  gem.add_development_dependency('bigdecimal')
 end