diff --git a/pulsar-functions/instance/src/main/java/org/apache/pulsar/functions/source/PulsarSource.java b/pulsar-functions/instance/src/main/java/org/apache/pulsar/functions/source/PulsarSource.java
index caaa7bf3f1ebb..9048544da615b 100644
--- a/pulsar-functions/instance/src/main/java/org/apache/pulsar/functions/source/PulsarSource.java
+++ b/pulsar-functions/instance/src/main/java/org/apache/pulsar/functions/source/PulsarSource.java
@@ -128,7 +128,7 @@ public void close() throws Exception {
 
     private void setupSerde() throws ClassNotFoundException {
 
-        Class<?> typeArg = Class.forName(this.pulsarConfig.getTypeClassName());
+        Class<?> typeArg = Thread.currentThread().getContextClassLoader().loadClass(this.pulsarConfig.getTypeClassName());
         if (Void.class.equals(typeArg)) {
             throw new RuntimeException("Input type of Pulsar Function cannot be Void");
         }