diff --git a/Library/Homebrew/cask/cask_loader.rb b/Library/Homebrew/cask/cask_loader.rb
index fdc2d158d9..2f2be8c66d 100644
--- a/Library/Homebrew/cask/cask_loader.rb
+++ b/Library/Homebrew/cask/cask_loader.rb
@@ -440,6 +440,10 @@ module Cask
     # Loader which tries loading casks from tap paths, failing
     # if the same token exists in multiple taps.
     class FromNameLoader < FromPathLoader
+      sig {
+        params(ref: T.any(String, Pathname, Cask, URI::Generic), warn: T::Boolean)
+          .returns(T.nilable(T.attached_class))
+      }
       def self.try_new(ref, warn: false)
         return unless ref.is_a?(String)
         return if ref.include?("/")
@@ -473,7 +477,13 @@ module Cask
 
     # Loader which loads a cask from the installed cask file.
     class FromInstalledPathLoader < FromPathLoader
+      sig {
+        params(ref: T.any(String, Pathname, Cask, URI::Generic), warn: T::Boolean)
+          .returns(T.nilable(T.attached_class))
+      }
       def self.try_new(ref, warn: false)
+        return unless ref.is_a?(String)
+
         possible_installed_cask = Cask.new(ref)
         return unless (installed_caskfile = possible_installed_cask.installed_caskfile)