diff --git a/src/collab/server/instance.js b/src/collab/server/instance.js
index 5d1510f..3a58e86 100644
--- a/src/collab/server/instance.js
+++ b/src/collab/server/instance.js
@@ -188,7 +188,7 @@ function doSave() {
       users: Array.from(instances[prop].users.values()),
       chat: instances[prop].chat.messages
     }
-  writeFile(saveFile, JSON.stringify(out))
+  writeFile(saveFile, JSON.stringify(out), (err) => { if (err) throw err; })
 }
 
 export function getInstance(id, clientId) {