msgpack_rails.gemspec in msgpack_rails-0.4.2 vs msgpack_rails.gemspec in msgpack_rails-0.4.3

@@ -25,7 +25,7 @@
     spec.add_runtime_dependency "msgpack"
   end
 
   spec.add_development_dependency "rake", "~> 10.3.1"
   spec.add_development_dependency "minitest", "~> 5.3.3"
-  spec.add_development_dependency "activemodel", "~> 4.1.0"
+  spec.add_development_dependency "rails", ">= 4.1.0"
 end