diff --git a/app/models/metadata_template.rb b/app/models/metadata_template.rb
index 89fd8315..03d42339 100644
--- a/app/models/metadata_template.rb
+++ b/app/models/metadata_template.rb
@@ -161,7 +161,7 @@ MetadataTemplate = Struct.new(:site, :document, :name, :label, :type,
   # once => el campo solo se puede modificar si estaba vacío
   def writable?
     case layout.metadata.dig(name, 'writable')
-    when 'once' then value.blank?
+    when 'once' then value_was.blank?
     else true
     end
   end