diff --git a/OpenEphys.Onix1/HarpSyncInputDataFrame.cs b/OpenEphys.Onix1/HarpSyncInputDataFrame.cs
index 9a3315e..65ec54b 100644
--- a/OpenEphys.Onix1/HarpSyncInputDataFrame.cs
+++ b/OpenEphys.Onix1/HarpSyncInputDataFrame.cs
@@ -18,7 +18,7 @@ public unsafe HarpSyncInputDataFrame(oni.Frame frame)
         {
             var payload = (HarpSyncInputPayload*)frame.Data.ToPointer();
             HubClock = payload->HubClock;
-            HarpTime = payload->HarpTime;
+            HarpTime = payload->HarpTime + 1;
         }
 
         /// <summary>