diff --git a/core/proto/android/stats/dnsresolver/dns_resolver.proto b/core/proto/android/stats/dnsresolver/dns_resolver.proto
index 448c12dd8d293..61b9b25fe7cf4 100644
--- a/core/proto/android/stats/dnsresolver/dns_resolver.proto
+++ b/core/proto/android/stats/dnsresolver/dns_resolver.proto
@@ -62,6 +62,13 @@ enum NsRcode {
     NS_R_NOTAUTH = 9;   // Not authoritative for zone
     NS_R_NOTZONE = 10;  // Zone of record different from zone section
     NS_R_MAX = 11;
+    // Define rcode=12~15(UNASSIGNED) in rcode enum type.
+    // Some DNS Servers might return undefined code to devices.
+    // Without the enum definition, that would be noise for our dashboard.
+    NS_R_UNASSIGNED12 = 12; // Unassigned
+    NS_R_UNASSIGNED13 = 13; // Unassigned
+    NS_R_UNASSIGNED14 = 14; // Unassigned
+    NS_R_UNASSIGNED15 = 15; // Unassigned
     // The following are EDNS extended rcodes
     NS_R_BADVERS = 16;
     // The following are TSIG errors