diff --git a/Library/Homebrew/cmd/leaves.rb b/Library/Homebrew/cmd/leaves.rb
index e3a3237247..e6fe1abd58 100644
--- a/Library/Homebrew/cmd/leaves.rb
+++ b/Library/Homebrew/cmd/leaves.rb
@@ -2,6 +2,7 @@
 # frozen_string_literal: true
 
 require "formula"
+require "cask_dependent"
 require "cli/parser"
 
 module Homebrew