--- a/toolkit/content/l20n-chrome-xul.js
+++ b/toolkit/content/l20n-chrome-xul.js
@@ -332,17 +332,17 @@ function entityFromContext(ctx, id, args
   const formatted = {
     value,
     attrs: null,
   };
 
   if (entity.traits) {
     formatted.attrs = Object.create(null);
     for (let trait of entity.traits) {
-      const [attrValue, attrErrors] = ctx.format(trait, args);
+      const [attrValue, attrErrors] = ctx.format(trait.val, args);
       errors.push(...attrErrors);
       formatted.attrs[trait.key.name] = attrValue;
     }
   }
 
   return [formatted, errors];
 }