diff --git a/Library/Homebrew/cmd/autoremove.rb b/Library/Homebrew/cmd/autoremove.rb
index 17d4781f8f..a80cb4ae49 100644
--- a/Library/Homebrew/cmd/autoremove.rb
+++ b/Library/Homebrew/cmd/autoremove.rb
@@ -36,10 +36,10 @@ module Homebrew
     removable_formulae = get_removable_formulae(Formula.installed)
 
     if (casks = Cask::Caskroom.casks.presence)
-      cask_formulae = casks.flat_map { |cask| cask.depends_on[:formula] }
-                           .compact
-                           .map { |formula| Formula[formula] }
-      removable_formulae -= [*cask_formulae, *cask_formulae.flat_map(&:runtime_formula_dependencies)]
+      removable_formulae -= casks.flat_map { |cask| cask.depends_on[:formula] }
+                                 .compact
+                                 .map { |f| Formula[f] }
+                                 .flat_map { |f| [f, *f.runtime_formula_dependencies].compact }
     end
     return if removable_formulae.blank?