diff --git a/src/sandbox/common.ts b/src/sandbox/common.ts
index ac450c9..83530fc 100644
--- a/src/sandbox/common.ts
+++ b/src/sandbox/common.ts
@@ -40,12 +40,13 @@ export function getTargetValue(target: any, value: any): any {
 
     const boundValue = Function.prototype.bind.call(value, target);
 
-    // some callable function has custom fields, we need to copy the enumerable props to boundValue. such as moment function.
-    // use for..in rather than Object.keys.forEach for performance reason
-    // eslint-disable-next-line guard-for-in,no-restricted-syntax
-    for (const key in value) {
-      boundValue[key] = value[key];
-    }
+    // some callable function has custom fields, we need to copy the own props to boundValue. such as moment function.
+    Object.getOwnPropertyNames(value).forEach((key) => {
+      // boundValue might be a proxy, we need to check the key whether exist in it
+      if (!boundValue.hasOwnProperty(key)) {
+        Object.defineProperty(boundValue, key, Object.getOwnPropertyDescriptor(value, key)!);
+      }
+    });
 
     // copy prototype if bound function not have but target one have
     // as prototype is non-enumerable mostly, we need to copy it from target function manually