diff --git a/backend/app/commands.py b/backend/app/commands.py
index f65be63..4abb95e 100644
--- a/backend/app/commands.py
+++ b/backend/app/commands.py
@@ -119,7 +119,11 @@ def start_proxmox_backup(
         "--output-format",
         "json",
     ]
-    result = run(command, timeout=300)
+    # pvesh create for vzdump blocks and streams the task log until the backup
+    # finishes rather than returning a UPID immediately, so this must not have
+    # a fixed timeout: it can legitimately run as long as the guest's backup
+    # takes (a prior 300s timeout was killing real, in-progress vzdump jobs).
+    result = run(command, timeout=None)
     upid = _extract_upid(result.stdout)
     if not upid:
         upid = _extract_upid(result.stderr)