diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index 19ef6a0196..fbc6c07b72 100644
--- a/tools/libxl/libxl.c
+++ b/tools/libxl/libxl.c
@@ -1207,7 +1207,8 @@ int libxl_device_nic_add(libxl_ctx *ctx, uint32_t domid, libxl_device_nic *nic)
             goto out_free;
         }
         if (!(l = libxl__xs_directory(&gc, XBT_NULL,
-                                     libxl__sprintf(&gc, "%s/device/vif", dompath), &nb))) {
+                                     libxl__sprintf(gc, "%s/device/vif", dompath), &nb)) ||
+            nb == 0) {
             nic->devid = 0;
         } else {
             nic->devid = strtoul(l[nb - 1], NULL, 10) + 1;