diff --git a/src/fu-device.c b/src/fu-device.c
index 8f9aa94fe..5b6e03238 100644
--- a/src/fu-device.c
+++ b/src/fu-device.c
@@ -446,6 +446,9 @@ fu_device_add_child (FuDevice *self, FuDevice *child)
 	g_ptr_array_add (priv->children, g_object_ref (child));
 
 	/* copy from main device if unset */
+	if (fu_device_get_physical_id (child) == NULL &&
+	    fu_device_get_physical_id (self) != NULL)
+		fu_device_set_physical_id (child, fu_device_get_physical_id (self));
 	if (fu_device_get_vendor (child) == NULL)
 		fu_device_set_vendor (child, fu_device_get_vendor (self));
 	if (fu_device_get_vendor_id (child) == NULL)