diff --git a/acts_as_follower.gemspec b/acts_as_follower.gemspec
index 642d7fc..a945ffd 100644
--- a/acts_as_follower.gemspec
+++ b/acts_as_follower.gemspec
@@ -20,7 +20,7 @@ Gem::Specification.new do |s|
 
   s.add_development_dependency "sqlite3"
   s.add_development_dependency "shoulda_create"
-  s.add_development_dependency "shoulda", "3.5.0"
-  s.add_development_dependency "factory_girl", "4.2.0"
+  s.add_development_dependency "shoulda", ">= 3.5.0"
+  s.add_development_dependency "factory_girl", ">= 4.2.0"
   s.add_development_dependency "rails", "~> 4.0.0"
 end