diff --git a/DnsServerCore/Dns/Zones/CacheZone.cs b/DnsServerCore/Dns/Zones/CacheZone.cs
index 90ea3c92..9675f2f3 100644
--- a/DnsServerCore/Dns/Zones/CacheZone.cs
+++ b/DnsServerCore/Dns/Zones/CacheZone.cs
@@ -76,14 +76,37 @@ namespace DnsServerCore.Dns.Zones
 
         public bool SetRecords(DnsResourceRecordType type, IReadOnlyList<DnsResourceRecord> records, bool serveStale)
         {
-            bool isFailureRecord = (records.Count > 0) && records[0].RDATA is DnsCache.DnsSpecialCacheRecord splRecord && splRecord.IsFailureOrBadCache;
-            if (isFailureRecord)
+            bool isFailureRecord = false;
+
+            if (records.Count > 0)
             {
-                //call trying to cache failure record
-                if (_entries.TryGetValue(type, out IReadOnlyList<DnsResourceRecord> existingRecords))
+                if (records[0].RDATA is DnsCache.DnsSpecialCacheRecord splRecord)
                 {
-                    if ((existingRecords.Count > 0) && !(existingRecords[0].RDATA is DnsCache.DnsSpecialCacheRecord existingSplRecord && existingSplRecord.IsFailureOrBadCache) && !DnsResourceRecord.IsRRSetExpired(existingRecords, serveStale))
-                        return false; //skip to avoid overwriting a useful record with a failure record
+                    if (splRecord.IsFailureOrBadCache)
+                    {
+                        //call trying to cache failure record
+                        isFailureRecord = true;
+
+                        if (_entries.TryGetValue(type, out IReadOnlyList<DnsResourceRecord> existingRecords))
+                        {
+                            if ((existingRecords.Count > 0) && !(existingRecords[0].RDATA is DnsCache.DnsSpecialCacheRecord existingSplRecord && existingSplRecord.IsFailureOrBadCache) && !DnsResourceRecord.IsRRSetExpired(existingRecords, serveStale))
+                                return false; //skip to avoid overwriting a useful record with a failure record
+                        }
+                    }
+                }
+                else if ((type == DnsResourceRecordType.NS) && (records[0].RDATA is DnsNSRecordData ns) && !ns.IsParentSideTtlSet)
+                {
+                    //for ns revalidation
+                    if (_entries.TryGetValue(DnsResourceRecordType.NS, out IReadOnlyList<DnsResourceRecord> existingNSRecords))
+                    {
+                        if ((existingNSRecords.Count > 0) && (existingNSRecords[0].RDATA is DnsNSRecordData existingNS) && existingNS.IsParentSideTtlSet)
+                        {
+                            uint parentSideTtl = existingNS.ParentSideTtl;
+
+                            foreach (DnsResourceRecord record in records)
+                                (record.RDATA as DnsNSRecordData).ParentSideTtl = parentSideTtl;
+                        }
+                    }
                 }
             }
 
@@ -201,7 +224,12 @@ namespace DnsServerCore.Dns.Zones
                     List<DnsResourceRecord> anyRecords = new List<DnsResourceRecord>(_entries.Count * 2);
 
                     foreach (KeyValuePair<DnsResourceRecordType, IReadOnlyList<DnsResourceRecord>> entry in _entries)
+                    {
+                        if (entry.Key == DnsResourceRecordType.DS)
+                            continue;
+
                         anyRecords.AddRange(ValidateRRSet(type, entry.Value, serveStale, true));
+                    }
 
                     return anyRecords;