diff --git a/Library/Homebrew/cmd/tap.rb b/Library/Homebrew/cmd/tap.rb
index 8dab836970..8fe4f1a5be 100644
--- a/Library/Homebrew/cmd/tap.rb
+++ b/Library/Homebrew/cmd/tap.rb
@@ -45,6 +45,7 @@ module Homebrew
     end
   end
 
+  sig { void }
   def tap
     args = tap_args.parse