diff --git a/DnsServerCore/Dns/ResourceRecords/DnsResourceRecordInfo.cs b/DnsServerCore/Dns/ResourceRecords/DnsResourceRecordInfo.cs
index 8055c1e1..a1ffd11a 100644
--- a/DnsServerCore/Dns/ResourceRecords/DnsResourceRecordInfo.cs
+++ b/DnsServerCore/Dns/ResourceRecords/DnsResourceRecordInfo.cs
@@ -222,7 +222,7 @@ namespace DnsServerCore.Dns.ResourceRecords
             get { return _comments; }
             set
             {
-                if (value.Length > 255)
+                if ((value is not null) && (value.Length > 255))
                     throw new ArgumentOutOfRangeException(nameof(Comments), "Resource record comment text cannot exceed 255 characters.");
 
                 _comments = value;