diff --git a/simple_form_objects.gemspec b/simple_form_objects.gemspec
index 42f3233..d984cd1 100644
--- a/simple_form_objects.gemspec
+++ b/simple_form_objects.gemspec
@@ -18,9 +18,9 @@ Gem::Specification.new do |spec|
   spec.test_files    = spec.files.grep(%r{^(test|spec|features)/})
   spec.require_paths = ["lib"]
 
-  spec.add_dependency "activemodel", "~> 4.0"
-  spec.add_dependency "activesupport", "~> 4.0"
-  spec.add_development_dependency "bundler", "~> 1.5"
+  spec.add_dependency "activemodel", ">= 4.0"
+  spec.add_dependency "activesupport", ">= 4.0"
+  spec.add_development_dependency "bundler", ">= 1.5"
   spec.add_development_dependency "rake"
   spec.add_development_dependency "rspec"
 end