diff --git a/src/modules/AdminModule.cpp b/src/modules/AdminModule.cpp
index 9be681b42f..4fae5b1432 100644
--- a/src/modules/AdminModule.cpp
+++ b/src/modules/AdminModule.cpp
@@ -1112,7 +1112,7 @@ void AdminModule::handleSetConfig(const meshtastic_Config &c, bool fromOthers)
                     //  Default root is in use, so subscribe to the appropriate MQTT topic for this region
                     snprintf(moduleConfig.mqtt.root, sizeof(moduleConfig.mqtt.root), "%s/%s", default_mqtt_root, myRegion->name);
                 }
-                changes = SEGMENT_CONFIG | SEGMENT_MODULECONFIG;
+                changes |= SEGMENT_CONFIG | SEGMENT_MODULECONFIG;
             }
             //  use_preset and bandwidth are coerced into valid values by the check.
         }
diff --git a/src/mqtt/MQTT.cpp b/src/mqtt/MQTT.cpp
index 8108ba050c..e8b9010f6a 100644
--- a/src/mqtt/MQTT.cpp
+++ b/src/mqtt/MQTT.cpp
@@ -374,6 +374,23 @@ void mqttInit()
     new MQTT();
 }
 
+void MQTT::reinitTopics()
+{
+    topicRoot = moduleConfig.mqtt.root;
+    const std::string root = *moduleConfig.mqtt.root ? moduleConfig.mqtt.root : default_mqtt_root;
+    cryptTopic = root + "/2/e/";
+    mapTopic = root + "/2/map/";
+    isConfiguredForDefaultRootTopic = isDefaultRootTopic(moduleConfig.mqtt.root);
+
+#if HAS_NETWORKING
+    // Force a broker reconnect so subscriptions are refreshed with the new topic prefix
+    if (pubSub.connected()) {
+        pubSub.disconnect();
+    }
+    isConnected = false;
+#endif
+}
+
 #if HAS_NETWORKING
 MQTT::MQTT() : MQTT(std::unique_ptr<MQTTClient>(new MQTTClient())) {}
 MQTT::MQTT(std::unique_ptr<MQTTClient> _mqttClient)
@@ -388,15 +405,7 @@ MQTT::MQTT() : concurrency::OSThread("mqtt"), mqttQueue(MAX_MQTT_QUEUE)
         assert(!mqtt);
         mqtt = this;
 
-        if (*moduleConfig.mqtt.root) {
-            cryptTopic = moduleConfig.mqtt.root + cryptTopic;
-            mapTopic = moduleConfig.mqtt.root + mapTopic;
-            isConfiguredForDefaultRootTopic = isDefaultRootTopic(moduleConfig.mqtt.root);
-        } else {
-            cryptTopic = "msh" + cryptTopic;
-            mapTopic = "msh" + mapTopic;
-            isConfiguredForDefaultRootTopic = true;
-        }
+        reinitTopics();
 
         if (moduleConfig.mqtt.map_reporting_enabled && moduleConfig.mqtt.has_map_report_settings) {
             map_position_precision = Default::getConfiguredOrDefault(moduleConfig.mqtt.map_report_settings.position_precision,
@@ -572,6 +581,9 @@ int32_t MQTT::runOnce()
 {
     if (!moduleConfig.mqtt.enabled || !(moduleConfig.mqtt.map_reporting_enabled || channels.anyMqttEnabled()))
         return disable();
+    // A region change rewrites the root at runtime, from several call sites
+    if (topicRoot != moduleConfig.mqtt.root)
+        reinitTopics();
     bool wantConnection = wantsLink();
 
     perhapsReportToMap();
@@ -762,6 +774,8 @@ void MQTT::onSend(const meshtastic_MeshPacket &mp_encrypted, const meshtastic_Me
                                             .channel_id = const_cast<char *>(channelId),
                                             .gateway_id = const_cast<char *>(nodeId.c_str())};
     size_t numBytes = pb_encode_to_bytes(bytes, sizeof(bytes), &meshtastic_ServiceEnvelope_msg, &env);
+    if (topicRoot != moduleConfig.mqtt.root)
+        reinitTopics(); // root changed before runOnce() noticed
     std::string topic = cryptTopic + channelId + "/" + nodeId;
 
     if (moduleConfig.mqtt.proxy_to_client_enabled || this->isConnectedDirectly()) {
diff --git a/src/mqtt/MQTT.h b/src/mqtt/MQTT.h
index 2851efc6dd..5a905433c8 100644
--- a/src/mqtt/MQTT.h
+++ b/src/mqtt/MQTT.h
@@ -98,6 +98,7 @@ class MQTT : private concurrency::OSThread
     explicit MQTT(std::unique_ptr<MQTTClient> mqttClient);
 #endif
 
+    std::string topicRoot;            // moduleConfig.mqtt.root the topics below were built from
     std::string cryptTopic = "/2/e/"; // msh/2/e/CHANNELID/NODEID
     std::string mapTopic = "/2/map/"; // For protobuf-encoded MapReport messages
 
@@ -111,6 +112,9 @@ class MQTT : private concurrency::OSThread
      */
     void reconnect();
 
+    /// Rebuild topics from moduleConfig.mqtt.root and force a resubscribe.
+    void reinitTopics();
+
     /** Tell the server what subscriptions we want (based on channels.downlink_enabled)
      */
     void sendSubscriptions();
diff --git a/test/test_mqtt/MQTT.cpp b/test/test_mqtt/MQTT.cpp
index 4d2ea6c268..0229c0fe59 100644
--- a/test/test_mqtt/MQTT.cpp
+++ b/test/test_mqtt/MQTT.cpp
@@ -1360,6 +1360,35 @@ void test_customMqttRoot(void)
         [] { return pubsub->subscriptions_.count("custom/2/e/test/+") && pubsub->subscriptions_.count("custom/2/e/PKI/+"); }));
 }
 
+// A LoRa region change rewrites moduleConfig.mqtt.root without telling MQTT (AdminModule, MenuHandler,
+// InkHUD). MQTT must pick it up, rebuild the topics and resubscribe; otherwise the node keeps
+// publishing and subscribing under the old region's root until reboot. An uplink sent before
+// runOnce() runs must already use the new root.
+void test_rootChange_rebuildsTopics(void)
+{
+    // Start MQTT with a US region root.
+    strcpy(moduleConfig.mqtt.root, "msh/US");
+    MQTTUnitTest::restart();
+
+    TEST_ASSERT_TRUE(loopUntil(
+        [] { return pubsub->subscriptions_.count("msh/US/2/e/test/+") && pubsub->subscriptions_.count("msh/US/2/e/PKI/+"); }));
+
+    // Simulate region change: only the root changes, nobody notifies MQTT.
+    strcpy(moduleConfig.mqtt.root, "msh/EU_868");
+    pubsub->subscriptions_.clear();
+    pubsub->published_.clear();
+    mqtt->onSend(encrypted, decoded, 0);
+
+    // Subscriptions are refreshed, and the uplink is published under the new root after the reconnect.
+    TEST_ASSERT_TRUE(loopUntil([] {
+        return pubsub->subscriptions_.count("msh/EU_868/2/e/test/+") && pubsub->subscriptions_.count("msh/EU_868/2/e/PKI/+") &&
+               !pubsub->published_.empty();
+    }));
+    TEST_ASSERT_EQUAL(1, pubsub->published_.size());
+    const auto &[topic, payload] = pubsub->published_.front();
+    TEST_ASSERT_EQUAL_STRING("msh/EU_868/2/e/test/!12345678", topic.c_str());
+}
+
 // Empty configuration is valid.
 void test_configEmptyIsValid(void)
 {
@@ -1555,6 +1584,7 @@ void setup()
     RUN_TEST(test_disabled);
     RUN_TEST(test_mqttInitSkipsAllocationWhenDisabled);
     RUN_TEST(test_customMqttRoot);
+    RUN_TEST(test_rootChange_rebuildsTopics);
     RUN_TEST(test_configEmptyIsValid);
     RUN_TEST(test_configEnabledEmptyIsValid);
     RUN_TEST(test_configWithDefaultServer);