diff --git a/Gemfile b/Gemfile
index dfc4c69..ecbb687 100644
--- a/Gemfile
+++ b/Gemfile
@@ -4,5 +4,5 @@ source "http://rubygems.org"
 gemspec
 
 group :test do
-  gem 'coveralls', :require => false
+  gem 'coveralls', :require => false, :platforms => [:ruby_19, :ruby_20]
 end