How to lock down CocoaPod library version?

There are currently newer versions of libraries I have specified in my Podfile which break our applications build . It happens when you perform a pod update. This is because our Podfile has fuzzy matching versions specified for some of the libraries. We need to lock these down to specific versions , example I have AFNetworking, '~> 1.0 in my pod file , When I perform a "pod update" then it install AFNetworking', '~> 1.3.3 , but I wanted lock down library to 1.0 only.