Conflicting CocoaPod name from two sources

When using two sources in our Podfile we are getting a collision with a CocoaPod that exists in the main spec repository and also in our private spec repository. Example Podfile assuming we have a private AFNetworking CocoaPod that we'd prefer to use:

source 'https://github.com/CocoaPods/Specs.git'
source 'https://github.com/PersonalSpecs/Specs.git'

use_frameworks!

target :MyTarget do
    platform :ios, '8.1'
    pod 'AFNetworking'
end

When we run pod install with this Podfile, CocoaPods ends up choosing the spec that exists in the main spec repository instead of our own.

I don't want to specify the git path for the pod since that avoids our normal spec publishing process. I've also tried altering the order of the source definitions.

Can we do anything to make CocoaPods use our private spec repository as the source for a given pod inclusion?

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