diff --git a/src/main/jastadd/backend/Mappings.jrag b/src/main/jastadd/backend/Mappings.jrag
index fd40385d9e8879dd188362f6a0acd802652f511e..600ce92ee064f45fe0f41860dd3ab0bc5e334bd3 100644
--- a/src/main/jastadd/backend/Mappings.jrag
+++ b/src/main/jastadd/backend/Mappings.jrag
@@ -111,7 +111,7 @@ aspect Mappings {
     //  or if no mappings are specified.
     // then prepend the suitable default mapping
     java.util.List<MappingDefinition> result;
-    if (getMappingList().size() == 0 || !getMappingList().get(0).getFromType().isByteArray()) {
+    if (getMappingList().isEmpty() || !getMappingList().get(0).getFromType().isByteArray()) {
       result = new java.util.ArrayList();
       result.add(suitableDefaultMapping());
       result.addAll(getMappingList());
@@ -161,7 +161,9 @@ aspect Mappings {
   // --- suitableDefaultMapping ---
   syn DefaultMappingDefinition UpdateDefinition.suitableDefaultMapping();
   eq ReadFromMqttDefinition.suitableDefaultMapping() {
-    String typeName = getToken().getJavaTypeUse().getName();
+    String typeName = getMappingList().isEmpty() ?
+        getToken().getJavaTypeUse().getName() :
+        getMappingList().get(0).getFromType().prettyPrint();
     switch(typeName) {
       case "int":
       case "Integer": return ros2rag().defaultBytesToIntMapping();
@@ -180,7 +182,9 @@ aspect Mappings {
     }
   }
   eq WriteToMqttDefinition.suitableDefaultMapping() {
-    String typeName = getToken().getJavaTypeUse().getName();
+    String typeName = getMappingList().isEmpty() ?
+        getToken().getJavaTypeUse().getName() :
+        getMappingList().get(getMappingList().size() - 1).getFromType().prettyPrint();
     switch(typeName) {
       case "int":
       case "Integer": return ros2rag().defaultIntToBytesMapping();
diff --git a/src/main/resources/MqttHandler.jadd b/src/main/resources/MqttHandler.jadd
index 47005270a0cae49229d70760be5be694ea3ca20f..c3e98dc89377e6217946fafa54a9eb7ab7594c61 100644
--- a/src/main/resources/MqttHandler.jadd
+++ b/src/main/resources/MqttHandler.jadd
@@ -21,7 +21,7 @@ public class MqttHandler {
   private boolean sendWelcomeMessage = true;
   private org.fusesource.mqtt.client.QoS qos;
   /** Dispatch knowledge */
-  private final java.util.Map<String, java.util.function.Consumer<byte[]>> callbacks;
+  private final java.util.Map<String, java.util.List<java.util.function.Consumer<byte[]>>> callbacks;
 
   public MqttHandler() {
     this("Ros2Rag");
@@ -81,13 +81,15 @@ public class MqttHandler {
       @Override
       public void onPublish(org.fusesource.hawtbuf.UTF8Buffer topic, org.fusesource.hawtbuf.Buffer body, org.fusesource.mqtt.client.Callback<org.fusesource.mqtt.client.Callback<Void>> ack) {
         String topicString = topic.toString();
-        java.util.function.Consumer<byte[]> callback = callbacks.get(topicString);
-        if (callback == null) {
+        java.util.List<java.util.function.Consumer<byte[]>> callbackList = callbacks.get(topicString);
+        if (callbackList == null || callbackList.isEmpty()) {
           logger.debug("Got a message, but no callback to call. Forgot to unsubscribe?");
         } else {
           byte[] message = body.toByteArray();
 //          System.out.println("message = " + Arrays.toString(message));
-          callback.accept(message);
+          for (java.util.function.Consumer<byte[]> callback : callbackList) {
+            callback.accept(message);
+          }
         }
         ack.onSuccess(null);  // always acknowledge message
       }
@@ -163,27 +165,30 @@ public class MqttHandler {
 
   public void newConnection(String topic, java.util.function.Consumer<byte[]> callback) {
     if (!ready) {
-      // TODO should maybe be something more kind than throwing an exception here
+      // should maybe be something more kind than throwing an exception here
       throw new IllegalStateException("Updater not ready");
     }
     // register callback
-    callbacks.put(topic, callback);
+    if (callbacks.get(topic) == null) {
+      callbacks.put(topic, new java.util.ArrayList<>());
 
-    // subscribe at broker
-    org.fusesource.mqtt.client.Topic[] topicArray = { new org.fusesource.mqtt.client.Topic(topic, this.qos) };
-    connection.getDispatchQueue().execute(() -> {
-      connection.subscribe(topicArray, new org.fusesource.mqtt.client.Callback<byte[]>() {
-        @Override
-        public void onSuccess(byte[] qoses) {
-          logger.debug("Subscribed to {}, qoses: {}", topic, qoses);
-        }
+      // subscribe at broker
+      org.fusesource.mqtt.client.Topic[] topicArray = { new org.fusesource.mqtt.client.Topic(topic, this.qos) };
+      connection.getDispatchQueue().execute(() -> {
+        connection.subscribe(topicArray, new org.fusesource.mqtt.client.Callback<byte[]>() {
+          @Override
+          public void onSuccess(byte[] qoses) {
+            logger.debug("Subscribed to {}, qoses: {}", topic, qoses);
+          }
 
-        @Override
-        public void onFailure(Throwable cause) {
-          logger.error("Could not subscribe to {}", topic, cause);
-        }
+          @Override
+          public void onFailure(Throwable cause) {
+            logger.error("Could not subscribe to {}", topic, cause);
+          }
+        });
       });
-    });
+    }
+    callbacks.get(topic).add(callback);
   }
 
   /**
diff --git a/src/main/resources/mqtt.mustache b/src/main/resources/mqtt.mustache
index fb2b173c35cc802c5c5c661cf22ce331c20fbbae..d65ca944a9dc7e881ff75d89ea696d4bb1fe09fc 100644
--- a/src/main/resources/mqtt.mustache
+++ b/src/main/resources/mqtt.mustache
@@ -1,5 +1,6 @@
 aspect MQTT {
-  private MqttHandler {{rootNodeName}}.{{mqttHandlerField}} = new MqttHandler();
+  private String {{rootNodeName}}.MqttName() { return "Ros2Rag"; }
+  private MqttHandler {{rootNodeName}}.{{mqttHandlerField}} = new MqttHandler(MqttName());
   public void {{rootNodeName}}.{{mqttSetHostMethod}}(String host) throws java.io.IOException {
     {{mqttHandlerField}}.setHost(host);
   }