diff --git a/sdks/java/io/mqtt/src/main/java/org/apache/beam/sdk/io/mqtt/MqttIO.java b/sdks/java/io/mqtt/src/main/java/org/apache/beam/sdk/io/mqtt/MqttIO.java
index d0788cad2ae1..e1868e2c8461 100644
--- a/sdks/java/io/mqtt/src/main/java/org/apache/beam/sdk/io/mqtt/MqttIO.java
+++ b/sdks/java/io/mqtt/src/main/java/org/apache/beam/sdk/io/mqtt/MqttIO.java
@@ -610,27 +610,22 @@ public void populateDisplayData(DisplayData.Builder builder) {
     @Override
     public PDone expand(PCollection<InputT> input) {
       checkArgument(connectionConfiguration() != null, "connectionConfiguration can not be null");
-      final SerializableFunction<InputT, String> topicFn;
       if (dynamic()) {
         checkArgument(
             connectionConfiguration().getTopic() == null, "DynamicWrite can not have static topic");
-        topicFn = topicFn();
+        checkArgument(topicFn() != null, "topicFn can not be null");
       } else {
         checkArgument(connectionConfiguration().getTopic() != null, "topic can not be null");
-        final String topic = connectionConfiguration().getTopic();
-        topicFn = ignore -> topic;
       }
-
-      checkArgument(topicFn != null, "topicFn can not be null");
       checkArgument(payloadFn() != null, "payloadFn can not be null");
 
-      input.apply(
-          ParDo.of(new WriteFn<>(connectionConfiguration(), topicFn, payloadFn(), retained())));
+      input.apply(ParDo.of(new WriteFn<>(this)));
       return PDone.in(input.getPipeline());
     }
 
     private static class WriteFn<InputT> extends DoFn<InputT, Void> {
-      private final ConnectionConfiguration connectionConfiguration;
+
+      private final Write<InputT> spec;
       private final SerializableFunction<InputT, String> topicFn;
       private final SerializableFunction<InputT, byte[]> payloadFn;
       private final boolean retained;
@@ -638,21 +633,22 @@ private static class WriteFn<InputT> extends DoFn<InputT, Void> {
       private transient MQTT client;
       private transient BlockingConnection connection;
 
-      public WriteFn(
-          ConnectionConfiguration connectionConfiguration,
-          SerializableFunction<InputT, String> topicFn,
-          SerializableFunction<InputT, byte[]> payloadFn,
-          boolean retained) {
-        this.connectionConfiguration = connectionConfiguration;
-        this.topicFn = topicFn;
-        this.payloadFn = payloadFn;
-        this.retained = retained;
+      public WriteFn(Write<InputT> spec) {
+        this.spec = spec;
+        if (spec.dynamic()) {
+          this.topicFn = spec.topicFn();
+        } else {
+          String topic = spec.connectionConfiguration().getTopic();
+          this.topicFn = ignore -> topic;
+        }
+        this.payloadFn = spec.payloadFn();
+        this.retained = spec.retained();
       }
 
       @Setup
       public void createMqttClient() throws Exception {
         LOG.debug("Starting MQTT writer");
-        this.client = this.connectionConfiguration.createClient();
+        this.client = this.spec.connectionConfiguration().createClient();
         LOG.debug("MQTT writer client ID is {}", client.getClientId());
         this.connection = createConnection(client);
       }