--- a/toolkit/content/l20n-chrome-xul.js
+++ b/toolkit/content/l20n-chrome-xul.js
@@ -318,29 +318,30 @@ function entityFromContext(ctx, id, args
 
   if (entity === undefined) {
     return [
       { value: id, attrs: null },
       [new L10nError(`Unknown entity: ${id}`)]
     ];
   }
 
-  const [value, errors] = ctx.formatToPrimitive(entity, args);
+  const formattedValue = ctx.formatToPrimitive(entity, args);
+  const errors = formattedValue[1];
 
   const formatted = {
-    value,
+    value: formattedValue[0],
     attrs: null,
   };
 
   if (entity.traits) {
     formatted.attrs = Object.create(null);
     for (let trait of entity.traits) {
-      const [attrValue, attrErrors] = ctx.format(trait.val, args);
-      errors.push(...attrErrors);
-      formatted.attrs[trait.key.name] = attrValue;
+      const formattedTrait = ctx.format(trait.val, args);
+      errors.push(...formattedTrait[1]);
+      formatted.attrs[trait.key.name] = formattedTrait[0];
     }
   }
 
   return [formatted, errors];
 }
 
 const properties = new WeakMap();
 const contexts = new WeakMap();
@@ -364,17 +365,19 @@ class Localization {
 
   formatWithFallback(bundles, keys, method, prev) {
     const ctx = contexts.get(bundles[0]);
 
     if (!ctx) {
       return prev.map(tuple => tuple[0]);
     }
 
-    const [translations, errors] = keysFromContext(ctx, keys, method, prev);
+    const formattedTuples = keysFromContext(ctx, keys, method, prev);
+    const translations = formattedTuples[0];
+    const errors = formattedTuples[1];
 
     if (errors.length === 0) {
       return translations.map(tuple => tuple[0]);
     }
 
     if (typeof console !== 'undefined') {
       errors.forEach(e => console.warn(e)); // eslint-disable-line no-console
     }