diff --git a/lib/action_form.rb b/lib/action_form.rb
index f4778cd..ea95c96 100644
--- a/lib/action_form.rb
+++ b/lib/action_form.rb
@@ -11,6 +11,10 @@
 module ActionForm
   require_relative 'action_form/engine'
 
+  def self.external_validation_methods
+    @external_validation_methods ||= []
+  end
+
   def self.rails_buggy?
     Rails.gem_version >= Gem::Version.new('7.0.3')
   end
diff --git a/lib/action_form/form.rb b/lib/action_form/form.rb
index 5444d70..bda3ccc 100644
--- a/lib/action_form/form.rb
+++ b/lib/action_form/form.rb
@@ -128,7 +128,7 @@ def method_missing(method_sym, *arguments, &block) # rubocop:disable Style/Missi
       return if method_sym == :id=
 
       # call validates/validate class methods
-      if method_sym =~ /^validates?$/ || method_sym == :phony_normalize || method_sym == :libphone_normalize
+      if method_sym =~ /^validates?$/ || ActionForm.external_validation_methods.include?(method_sym)
         class_eval do
           public_send(method_sym, *arguments, &block)
         end