diff --git a/pulsar-functions/utils/src/main/java/org/apache/pulsar/functions/utils/FunctionConfigUtils.java b/pulsar-functions/utils/src/main/java/org/apache/pulsar/functions/utils/FunctionConfigUtils.java
index 824c1db63ff29cda15c679f198b71da24024f012..842da22f176d5301fba5ef6d8481761e198b67dd 100644
--- a/pulsar-functions/utils/src/main/java/org/apache/pulsar/functions/utils/FunctionConfigUtils.java
+++ b/pulsar-functions/utils/src/main/java/org/apache/pulsar/functions/utils/FunctionConfigUtils.java
@@ -632,9 +632,11 @@ public class FunctionConfigUtils {
         } else if (functionConfig.getRuntime() == FunctionConfig.Runtime.GO) {
             doGolangChecks(functionConfig);
             return null;
-        } else {
+        } else if (functionConfig.getRuntime() == FunctionConfig.Runtime.PYTHON){
             doPythonChecks(functionConfig);
             return null;
+        } else {
+            throw new IllegalArgumentException("Function language runtime is either not set or cannot be determined");
         }
     }
 
diff --git a/pulsar-functions/worker/src/test/java/org/apache/pulsar/functions/worker/rest/api/v3/FunctionApiV3ResourceTest.java b/pulsar-functions/worker/src/test/java/org/apache/pulsar/functions/worker/rest/api/v3/FunctionApiV3ResourceTest.java
index 4bb08c17ace9feecb22615b746a21c370457ea77..e5df566a5a18e6ad90f39ce1db71162e6dc42133 100644
--- a/pulsar-functions/worker/src/test/java/org/apache/pulsar/functions/worker/rest/api/v3/FunctionApiV3ResourceTest.java
+++ b/pulsar-functions/worker/src/test/java/org/apache/pulsar/functions/worker/rest/api/v3/FunctionApiV3ResourceTest.java
@@ -1533,6 +1533,31 @@ public class FunctionApiV3ResourceTest {
         resource.registerFunction(actualTenant, actualNamespace, actualName, null, null, filePackageUrl, functionConfig, null, null);
     }
 
+    @Test(expectedExceptions = RestException.class, expectedExceptionsMessageRegExp = "Function language runtime is either not set or cannot be determined")
+    public void testCreateFunctionWithoutSettingRuntime() {
+        Configurator.setRootLevel(Level.DEBUG);
+
+        String fileLocation = FutureUtil.class.getProtectionDomain().getCodeSource().getLocation().getPath();
+        String filePackageUrl = "file://" + fileLocation;
+        when(mockedManager.containsFunction(eq(tenant), eq(namespace), eq(function))).thenReturn(false);
+
+        RequestResult rr = new RequestResult().setSuccess(true).setMessage("function registered");
+        CompletableFuture<RequestResult> requestResult = CompletableFuture.completedFuture(rr);
+        when(mockedManager.updateFunction(any(FunctionMetaData.class))).thenReturn(requestResult);
+
+        FunctionConfig functionConfig = new FunctionConfig();
+        functionConfig.setTenant(tenant);
+        functionConfig.setNamespace(namespace);
+        functionConfig.setName(function);
+        functionConfig.setClassName(className);
+        functionConfig.setParallelism(parallelism);
+        functionConfig.setCustomSerdeInputs(topicsToSerDeClassName);
+        functionConfig.setOutput(outputTopic);
+        functionConfig.setOutputSerdeClassName(outputSerdeClassName);
+        resource.registerFunction(tenant, namespace, function, null, null, filePackageUrl, functionConfig, null, null);
+
+    }
+
     public static FunctionConfig createDefaultFunctionConfig() {
         FunctionConfig functionConfig = new FunctionConfig();
         functionConfig.setTenant(tenant);