diff --git a/Library/Homebrew/formulary.rb b/Library/Homebrew/formulary.rb
index 65858d3e43..df7bfff951 100644
--- a/Library/Homebrew/formulary.rb
+++ b/Library/Homebrew/formulary.rb
@@ -264,6 +264,7 @@ module Formulary
   end
 
   def self.convert_to_deprecate_disable_reason_string_or_symbol(string)
+    require "deprecate_disable"
     return string unless DeprecateDisable::DEPRECATE_DISABLE_REASONS.keys.map(&:to_s).include?(string)
 
     string.to_sym