diff --git a/rdkit.gemspec b/rdkit.gemspec
index 88795d7..7f32f4a 100644
--- a/rdkit.gemspec
+++ b/rdkit.gemspec
@@ -26,7 +26,7 @@ Gem::Specification.new do |spec|
   spec.add_runtime_dependency 'httpi'
   spec.add_runtime_dependency 'multi_json'
 
-  spec.add_development_dependency "bundler", "~> 1.8"
+  spec.add_development_dependency "bundler", "~> 2.1"
   spec.add_development_dependency "rake", "~> 10.0"
   spec.add_development_dependency "rspec"
 end