diff --git a/recurly.gemspec b/recurly.gemspec
index fa241aa4..504aee28 100644
--- a/recurly.gemspec
+++ b/recurly.gemspec
@@ -29,6 +29,8 @@ Gem::Specification.new do |spec|
   # spec.executables   = spec.files.grep(%r{^exe/}) { |f| File.basename(f) }
   spec.require_paths = ["lib"]
 
+  spec.add_dependency "base64", "~> 0.2.0"
+
   spec.add_development_dependency "bundler", "~> 2.0"
   spec.add_development_dependency "rake", "~> 12.3.3"
   spec.add_development_dependency "rspec", "~> 3.0"