diff --git a/misc/xl-qvm-usb-attach.py b/misc/xl-qvm-usb-attach.py
index e854229..58ac2a8 100755
--- a/misc/xl-qvm-usb-attach.py
+++ b/misc/xl-qvm-usb-attach.py
@@ -45,4 +45,4 @@ else:
     qvm_collection.unlock_db()
 
     # launch
-    qvm_collection.get_vm_by_name(backendvm_name).run("root: %s" % cmd)
+    qvm_collection.get_vm_by_name(backendvm_name).run(cmd, user="root")
diff --git a/misc/xl-qvm-usb-detach.py b/misc/xl-qvm-usb-detach.py
index 478d8bb..e32fe47 100755
--- a/misc/xl-qvm-usb-detach.py
+++ b/misc/xl-qvm-usb-detach.py
@@ -41,7 +41,7 @@ else:
     qvm_collection.unlock_db()
 
     # launch
-    qvm_collection.get_vm_by_name(backendvm_name).run("root: %s" % cmd)
+    qvm_collection.get_vm_by_name(backendvm_name).run(cmd, user="root")
 
 # FIXME: command injection
 os.system("xenstore-write /local/domain/%s/backend/vusb/%s/%s/port/%s ''"