diff --git a/github-linguist.gemspec b/github-linguist.gemspec
index 57a00235..6a06a6f2 100644
--- a/github-linguist.gemspec
+++ b/github-linguist.gemspec
@@ -17,7 +17,7 @@ Gem::Specification.new do |s|
   s.add_dependency 'escape_utils',    '~> 1.0.1'
   s.add_dependency 'mime-types',      '~> 1.19'
   s.add_dependency 'pygments.rb',     '~> 0.6.0'
-  s.add_dependency 'rugged',          '0.21.1b2'
+  s.add_dependency 'rugged',          '~> 0.21.1b2'
 
   s.add_development_dependency 'json'
   s.add_development_dependency 'mocha'