diff --git a/src/ts/@overflow/commons/invoke/ServiceInvoker.ts b/src/ts/@overflow/commons/invoke/ServiceInvoker.ts
index b232c68..d915448 100644
--- a/src/ts/@overflow/commons/invoke/ServiceInvoker.ts
+++ b/src/ts/@overflow/commons/invoke/ServiceInvoker.ts
@@ -7,7 +7,11 @@ export class ServiceInvoker {
     }
 
     public invoke(className: string, methodName: string, params?: any): void {
-        let classObj: Object = this.configMap[className];
+        let classObj: Object = this.configMap.get(className);
+        if (classObj === null) {
+            console.log('Error: Cannot find the class. [' + className + ']');
+            return;
+        }
         if (!classObj.hasOwnProperty(methodName)) {
             console.log('Error: Cannot find the method. [' + methodName + ']');
             return;