diff --git a/Library/Homebrew/style.rb b/Library/Homebrew/style.rb
index ca47f72043f13a74a719c12f4efafca6307081a7..c4886c6211760fd4df21d168b3d83ca5e9448d86 100644
--- a/Library/Homebrew/style.rb
+++ b/Library/Homebrew/style.rb
@@ -61,7 +61,7 @@ module Homebrew
       end
 
       if files && !has_non_formula
-        config = if (files.first/"spec").exist?
+        config = if files.first && File.exist?("#{files.first}/spec")
           HOMEBREW_LIBRARY/".rubocop_rspec.yml"
         else
           HOMEBREW_LIBRARY/".rubocop_audit.yml"