diff --git a/src/backupsites.js b/src/backupsites.js
index c511be5b0..fad4999da 100644
--- a/src/backupsites.js
+++ b/src/backupsites.js
@@ -492,6 +492,7 @@ async function setConfig(backupSite, newConfig, auditSource) {
 
     const oldConfig = backupSite.config;
 
+    newConfig = structuredClone(newConfig); // make a copy
     storageApi(backupSite).injectPrivateFields(newConfig, oldConfig);
 
     debug('setConfig: validating new storage configuration');