RealmSwift Dependency in pod spec

I have a project in which I used Realm, which has been installed by pruning (pod 'RealmSwift').

Now, I want to make a private pod of the product and put RealmSwift as a dependency to install when someone installs my pod.

I get the following error:

  

[!] Unable to find a specification for RealmSwift depended upon by SecureLocalStorage

Within the podspec, it is defined as follows:

spec.frameworks  = "RealmSwift"
spec.dependency 'RealmSwift'

Any ideas?