diff --git a/dns64.c b/dns64.c
index a9ca61d..ed28eb0 100644
--- a/dns64.c
+++ b/dns64.c
@@ -49,7 +49,7 @@
 
   // Be sure to query local DNS64 servers, bypassing Private DNS (if enabled).
   if (net_id != NETID_UNSET) {
-    net_id += NETID_USE_LOCAL_NAMESERVERS;
+    net_id |= NETID_USE_LOCAL_NAMESERVERS;
   }
 
   status = android_getaddrinfofornet(ipv4_name, NULL, &hints, net_id, MARK_UNSET, &result);