diff --git a/hw/ide/qdev.c b/hw/ide/qdev.c
index b4a467116e..efab95b320 100644
--- a/hw/ide/qdev.c
+++ b/hw/ide/qdev.c
@@ -59,7 +59,7 @@ static char *idebus_get_fw_dev_path(DeviceState *dev)
 {
     char path[30];
 
-    snprintf(path, sizeof(path), "%s@%d", qdev_fw_name(dev),
+    snprintf(path, sizeof(path), "%s@%x", qdev_fw_name(dev),
              ((IDEBus*)dev->parent_bus)->bus_id);
 
     return g_strdup(path);