diff --git a/Library/Homebrew/dev-cmd/sh.rb b/Library/Homebrew/dev-cmd/sh.rb
index 8de321c292..dbb8b8a878 100644
--- a/Library/Homebrew/dev-cmd/sh.rb
+++ b/Library/Homebrew/dev-cmd/sh.rb
@@ -46,7 +46,7 @@ module Homebrew
     if args.cmd.present?
       safe_system(ENV["SHELL"], "-c", args.cmd)
     elsif args.named.present?
-      safe_system(ENV["SHELL"], args.named[0])
+      safe_system(ENV["SHELL"], args.named.first)
     else
       subshell = if ENV["SHELL"].include?("zsh")
         "PS1='brew %B%F{green}%~%f%b$ ' #{ENV["SHELL"]} -d"