diff --git a/lib/structures/dict.js b/lib/structures/dict.js
index d43f0f7..2a3813d 100644
--- a/lib/structures/dict.js
+++ b/lib/structures/dict.js
@@ -23,6 +23,7 @@ export const fold = callback => initial => dict => {
   for (const iter=dict.tree.begin; iter !== undefined && iter.valid; iter.next()) {
     acc = callback(acc)(iter.key)(iter.value);
   }
+  return acc;
 }
 
 export const first = dict => dict.tree.begin;