diff --git a/libs/main/io_utils/piconnection.cpp b/libs/main/io_utils/piconnection.cpp
index 50f6e565..8b04f33a 100644
--- a/libs/main/io_utils/piconnection.cpp
+++ b/libs/main/io_utils/piconnection.cpp
@@ -1234,9 +1234,14 @@ void PIConnection::Sender::tick(int) {
 	if (data.isEmpty()) return;
 	// piCoutObj << "write"<<data.size()<<"bytes to"<<devices.size()<<"devices";
 	for (PIIODevice * d: devices) {
-		int ret              = d->write(data);
-		PIDiagnostics * diag = parent->diags_.value(d, nullptr);
-		if (diag && ret > 0) diag->sended(ret);
+		int ret = d->write(data);
+		if (ret > 0) {
+			PIDiagnostics * diag = nullptr;
+			__device_pool__->lock();
+			diag = parent->diags_.value(d, nullptr);
+			__device_pool__->unlock();
+			if (diag) diag->sended(ret);
+		}
 	}
 }