diff --git a/frontend/templates/index.html b/frontend/templates/index.html
index 985811c..4b3592a 100644
--- a/frontend/templates/index.html
+++ b/frontend/templates/index.html
@@ -419,6 +419,7 @@ async function copyVM(jobId, vmid, sourceFilename) {
   if (diskGb) payload.append('target_disk_size_gb', diskGb);
   payload.append('auto_detect_boot', 'true');
   payload.append('boot_type', 'uefi');
+  payload.append('session_id', window.VM_BENCH_SID || '');
   try {
     const resp = await fetch('/session/confirm', { method: 'POST', body: payload });
     const html = await resp.text();