diff --git a/js/src/common/Model.ts b/js/src/common/Model.ts
index 9cea14335..338b66207 100644
--- a/js/src/common/Model.ts
+++ b/js/src/common/Model.ts
@@ -110,6 +110,7 @@ export default abstract class Model {
     }
 
     if ('attributes' in data) {
+      this.data.attributes ||= {};
       Object.assign(this.data.attributes, data.attributes);
     }