diff --git a/Gemfile b/Gemfile
index dd0a01da..3eb7465d 100644
--- a/Gemfile
+++ b/Gemfile
@@ -1,5 +1,8 @@
 source 'https://rubygems.org'
 
+# rails-assets requires >= 1.8.4
+gem 'bundler', '>= 1.8.4'
+
 # as web framework
 gem 'rails', '~> 4.2'
 
diff --git a/Gemfile.lock b/Gemfile.lock
index f9ad33e9..e8700d76 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -506,6 +506,7 @@ DEPENDENCIES
   bootstrap-sass (~> 3.3.4.1)
   bootstrap-switch-rails (~> 3.0.0)
   bootstrap3-datetimepicker-rails (~> 3.0.2)
+  bundler (>= 1.8.4)
   byebug
   cancancan
   capybara