diff --git a/Library/Homebrew/tap.rb b/Library/Homebrew/tap.rb
index 58474c0613..babebecc5c 100644
--- a/Library/Homebrew/tap.rb
+++ b/Library/Homebrew/tap.rb
@@ -108,6 +108,11 @@ class Tap
     path.directory?
   end
 
+  # @private
+  def core_formula_repository?
+    false
+  end
+
   # install this {Tap}.
   #
   # @param [Hash] options
@@ -365,6 +370,11 @@ class CoreFormulaRepository < Tap
     remote != "https://github.com/#{user}/#{repo}.git"
   end
 
+  # @private
+  def core_formula_repository?
+    true
+  end
+
   # @private
   def formula_dir
     HOMEBREW_LIBRARY/"Formula"