diff --git a/Library/Homebrew/cmd/install.rb b/Library/Homebrew/cmd/install.rb
index ce319819f9..6bf3912b7c 100644
--- a/Library/Homebrew/cmd/install.rb
+++ b/Library/Homebrew/cmd/install.rb
@@ -401,7 +401,7 @@ module Homebrew
     build_options = f.build
 
     if !Homebrew::EnvConfig.no_install_upgrade? && f.outdated? && !f.head?
-      formulae = [f] + f.old_installed_formulae
+      formulae = [f, *f.old_installed_formulae]
       version_upgrade = "#{f.linked_version} -> #{f.pkg_version}"
 
       oh1 <<~EOS