diff --git a/DnsServerCore/Dns/ZoneManagers/BlockListZoneManager.cs b/DnsServerCore/Dns/ZoneManagers/BlockListZoneManager.cs
index 7c7eca1d..160f15a7 100644
--- a/DnsServerCore/Dns/ZoneManagers/BlockListZoneManager.cs
+++ b/DnsServerCore/Dns/ZoneManagers/BlockListZoneManager.cs
@@ -225,6 +225,8 @@ namespace DnsServerCore.Dns.ZoneManagers
 
         public void LoadBlockLists()
         {
+            Flush();
+
             //read all block lists in a queue
             Dictionary<Uri, Queue<string>> blockListQueues = new Dictionary<Uri, Queue<string>>(_blockListUrls.Count);
             int totalDomains = 0;