diff --git a/testable-agent/src/main/java/com/alibaba/testable/agent/handler/BaseClassHandler.java b/testable-agent/src/main/java/com/alibaba/testable/agent/handler/BaseClassHandler.java
index 05477cd..859a222 100644
--- a/testable-agent/src/main/java/com/alibaba/testable/agent/handler/BaseClassHandler.java
+++ b/testable-agent/src/main/java/com/alibaba/testable/agent/handler/BaseClassHandler.java
@@ -1,15 +1,9 @@
 package com.alibaba.testable.agent.handler;
 
-import com.alibaba.testable.agent.util.ClassUtil;
-import com.alibaba.testable.core.util.LogUtil;
 import org.objectweb.asm.ClassReader;
 import org.objectweb.asm.ClassWriter;
 import org.objectweb.asm.Opcodes;
 import org.objectweb.asm.tree.ClassNode;
-import org.objectweb.asm.tree.FieldNode;
-
-import java.io.IOException;
-import java.util.Iterator;
 
 /**
  * @author flin
@@ -23,26 +17,11 @@ abstract public class BaseClassHandler implements Opcodes {
 
     protected String mockClassName;
 
-    protected boolean markTransformed(ClassNode cn, String refName, String refDescriptor) {
-        Iterator<FieldNode> iterator = cn.fields.iterator();
-        if (iterator.hasNext()) {
-            if (refName.equals(iterator.next().name)) {
-                // avoid duplicate injection
-                LogUtil.verbose("Duplicate injection found, ignore " + cn.name);
-                return false;
-            }
-        }
-        cn.fields.add(new FieldNode(ACC_PRIVATE | ACC_STATIC, refName, refDescriptor, null, null));
-        return true;
-    }
-
-    public byte[] getBytes(byte[] classFileBuffer) throws IOException {
+    public byte[] getBytes(byte[] classFileBuffer) {
         ClassReader cr = new ClassReader(classFileBuffer);
         ClassNode cn = new ClassNode();
         cr.accept(cn, 0);
-        if (markTransformed(cn, TESTABLE_REF, ClassUtil.toByteCodeClassName(mockClassName))) {
-            transform(cn);
-        }
+        transform(cn);
         ClassWriter cw = new ClassWriter( 0);
         cn.accept(cw);
         return cw.toByteArray();
diff --git a/testable-agent/src/main/java/com/alibaba/testable/agent/handler/MockClassHandler.java b/testable-agent/src/main/java/com/alibaba/testable/agent/handler/MockClassHandler.java
index e6215ef..6594751 100644
--- a/testable-agent/src/main/java/com/alibaba/testable/agent/handler/MockClassHandler.java
+++ b/testable-agent/src/main/java/com/alibaba/testable/agent/handler/MockClassHandler.java
@@ -40,7 +40,7 @@ public class MockClassHandler extends BaseClassWithContextHandler {
 
     @Override
     protected void transform(ClassNode cn) {
-        injectGetInstanceMethod(cn);
+        injectRefFieldAndGetInstanceMethod(cn);
         for (MethodNode mn : cn.methods) {
             if (isMockMethod(mn)) {
                 mn.access &= ~ACC_PRIVATE;
@@ -61,25 +61,27 @@ public class MockClassHandler extends BaseClassWithContextHandler {
     /**
      * add method to fetch singleton instance of this mock class
      */
-    private void injectGetInstanceMethod(ClassNode cn) {
+    private void injectRefFieldAndGetInstanceMethod(ClassNode cn) {
+        String byteCodeMockClassName = ClassUtil.toByteCodeClassName(mockClassName);
         MethodNode getInstanceMethod = new MethodNode(ACC_PUBLIC | ACC_STATIC, GET_TESTABLE_REF,
-            VOID_ARGS + ClassUtil.toByteCodeClassName(mockClassName), null, null);
+            VOID_ARGS + byteCodeMockClassName, null, null);
         InsnList il = new InsnList();
-        il.add(new FieldInsnNode(GETSTATIC, mockClassName, TESTABLE_REF, ClassUtil.toByteCodeClassName(mockClassName)));
+        il.add(new FieldInsnNode(GETSTATIC, mockClassName, TESTABLE_REF, byteCodeMockClassName));
         LabelNode label = new LabelNode();
         il.add(new JumpInsnNode(IFNONNULL, label));
         il.add(new TypeInsnNode(NEW, mockClassName));
         il.add(new InsnNode(DUP));
         il.add(new MethodInsnNode(INVOKESPECIAL, mockClassName, CONSTRUCTOR, VOID_ARGS + VOID_RES, false));
-        il.add(new FieldInsnNode(PUTSTATIC, mockClassName, TESTABLE_REF, ClassUtil.toByteCodeClassName(mockClassName)));
+        il.add(new FieldInsnNode(PUTSTATIC, mockClassName, TESTABLE_REF, byteCodeMockClassName));
         il.add(label);
         il.add(new FrameNode(F_SAME, 0, null, 0, null));
-        il.add(new FieldInsnNode(GETSTATIC, mockClassName, TESTABLE_REF, ClassUtil.toByteCodeClassName(mockClassName)));
+        il.add(new FieldInsnNode(GETSTATIC, mockClassName, TESTABLE_REF, byteCodeMockClassName));
         il.add(new InsnNode(ARETURN));
         getInstanceMethod.instructions = il;
         getInstanceMethod.maxStack = 2;
         getInstanceMethod.maxLocals = 0;
         cn.methods.add(getInstanceMethod);
+        cn.fields.add(new FieldNode(ACC_PRIVATE | ACC_STATIC, TESTABLE_REF, byteCodeMockClassName, null, null));
     }
 
     /**