diff --git a/pulsar-functions/instance/src/main/python/python_instance.py b/pulsar-functions/instance/src/main/python/python_instance.py
index 6f74461e8532f..66d222c73cc08 100644
--- a/pulsar-functions/instance/src/main/python/python_instance.py
+++ b/pulsar-functions/instance/src/main/python/python_instance.py
@@ -272,7 +272,8 @@ def done_producing(self, consumer, orig_message, result, sent_message):
       consumer.acknowledge(orig_message)
 
   def process_result(self, output, msg):
-    if output is not None:
+    if output is not None and self.instance_config.function_details.sink.topic != None and \
+            len(self.instance_config.function_details.sink.topic) > 0:
       if self.output_serde is None:
         self.setup_output_serde()
       if self.producer is None: