diff --git a/src/ScadaLink.DataConnectionLayer/Adapters/LmxProxyDataConnection.cs b/src/ScadaLink.DataConnectionLayer/Adapters/LmxProxyDataConnection.cs
index b42bf09..6da1ef0 100644
--- a/src/ScadaLink.DataConnectionLayer/Adapters/LmxProxyDataConnection.cs
+++ b/src/ScadaLink.DataConnectionLayer/Adapters/LmxProxyDataConnection.cs
@@ -82,7 +82,11 @@ public class LmxProxyDataConnection : IDataConnection
 
         try
         {
-            _heartbeatSubscriptionId = await SubscribeAsync(heartbeatTag, (_, _) => _staleMonitor.OnValueReceived(), cancellationToken);
+            _heartbeatSubscriptionId = await SubscribeAsync(heartbeatTag, (tag, value) =>
+            {
+                _logger.LogDebug("LmxProxy heartbeat received: {Tag} = {Value} (quality={Quality})", tag, value.Value, value.Quality);
+                _staleMonitor.OnValueReceived();
+            }, cancellationToken);
             _staleMonitor.Start();
             _logger.LogInformation("LmxProxy heartbeat monitor started for '{Tag}' with {Seconds}s max silence", heartbeatTag, maxSilenceSeconds);
         }