diff --git a/abbterra/integrationpluginabbterra.cpp b/abbterra/integrationpluginabbterra.cpp
index 762181a..d7185eb 100644
--- a/abbterra/integrationpluginabbterra.cpp
+++ b/abbterra/integrationpluginabbterra.cpp
@@ -11,6 +11,7 @@
 #include "plugininfo.h"
 
 #include <QLoggingCategory>
+#include <QTimer>
 #include <QtMath>
 #include <utility>
 
@@ -332,6 +333,20 @@ void IntegrationPluginAbbterra::setupRtuThing(ThingSetupInfo *info)
     const quint16 slaveId = static_cast<quint16>(thing->paramValue(terraAcRtuThingSlaveIdParamTypeId).toUInt());
     AbbTerraModbusRtuConnection *connection = new AbbTerraModbusRtuConnection(master, slaveId, thing);
 
+    // reachableChanged(true) may never fire on slow radio links (e.g. 433 MHz)
+    // before the setup timeout expires, so we also trigger initialize() as soon
+    // as the master port is open.
+    if (master->connected()) {
+        QTimer::singleShot(500, connection, [connection]() {
+            connection->initialize();
+        });
+    }
+    connect(master, &ModbusRtuMaster::connectedChanged, connection, [connection](bool connected) {
+        if (connected) {
+            connection->initialize();
+        }
+    });
+
     connect(connection, &AbbTerraModbusRtuConnection::reachableChanged, thing, [this, thing, connection](bool reachable) {
         if (reachable) {
             connection->initialize();
diff --git a/debian/changelog b/debian/changelog
index b0f174e..6a288cb 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -1,3 +1,11 @@
+etm-powersync-plugins-modbus (1.15.0+etm5) trixie; urgency=medium
+
+  * abbterra: fix RTU setup on slow radio links — trigger initialize() on
+    master connectedChanged, not only on reachableChanged (which never fires
+    within setup timeout over 433 MHz).
+
+ -- ETM-Schurig SARL <contact@etm-schurig.eu>  Tue, 24 Jun 2026 10:00:00 +0200
+
 etm-powersync-plugins-modbus (1.15.0+etm4) trixie; urgency=medium
 
   * Correction modbus registers.