--- a/compat/backport-4.12.c
+++ b/compat/backport-4.12.c
@@ -224,6 +224,7 @@ int bp_extack_genl_register_family(struc
 	}
 
 	/* copy this since the family might access it directly */
+	family->id = copy->family.id;
 	family->attrbuf = copy->family.attrbuf;
 	family->mcgrp_offset = copy->family.mcgrp_offset;
 
