diff --git a/code-reviews/Driver.Historian.Wonderware/findings.md b/code-reviews/Driver.Historian.Wonderware/findings.md
index 86c70d1..bbfa113 100644
--- a/code-reviews/Driver.Historian.Wonderware/findings.md
+++ b/code-reviews/Driver.Historian.Wonderware/findings.md
@@ -63,7 +63,7 @@ the reconnect path can re-open with `ReadOnly = false`) or at minimum as
 | Severity | Medium |
 | Category | Correctness and logic bugs |
 | Location | `Ipc/HistorianFrameHandler.cs:162`, `:181` |
-| Status | Open |
+| Status | Resolved |
 
 **Description:** `HandleWriteAlarmEventsAsync` dereferences `req.Events.Length`
 in both the `_alarmWriter is null` branch (line 162) and the catch block (line
@@ -79,7 +79,7 @@ already null-guards `events`; the frame handler does not.
 immediately after deserialization (or guard each `.Length` access), consistent
 with the null-tolerance the writer already has.
 
-**Resolution:** _(open)_
+**Resolution:** Resolved 2026-05-22 — normalise `req.Events` to `Array.Empty<AlarmHistorianEventDto>()` immediately after deserialization so all subsequent `.Length` accesses are safe against null frames.
 
 ### Driver.Historian.Wonderware-003
 
diff --git a/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Wonderware/Ipc/HistorianFrameHandler.cs b/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Wonderware/Ipc/HistorianFrameHandler.cs
index da85830..3779803 100644
--- a/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Wonderware/Ipc/HistorianFrameHandler.cs
+++ b/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Historian.Wonderware/Ipc/HistorianFrameHandler.cs
@@ -153,6 +153,11 @@ public sealed class HistorianFrameHandler : IFrameHandler
     private async Task HandleWriteAlarmEventsAsync(byte[] body, FrameWriter writer, CancellationToken ct)
     {
         var req = MessagePackSerializer.Deserialize<WriteAlarmEventsRequest>(body);
+
+        // MessagePack deserializes an absent or explicit-nil array as null, not Array.Empty.
+        // Normalise here so every path below can safely dereference .Length without an NRE.
+        req.Events ??= Array.Empty<AlarmHistorianEventDto>();
+
         var reply = new WriteAlarmEventsReply { CorrelationId = req.CorrelationId };
 
         if (_alarmWriter is null)