diff --git a/src/v3/reactivity/readonly.ts b/src/v3/reactivity/readonly.ts
index 933f910b69f..f3c0b3a9331 100644
--- a/src/v3/reactivity/readonly.ts
+++ b/src/v3/reactivity/readonly.ts
@@ -70,7 +70,11 @@ function createReadonly(target: any, shallow: boolean) {
   }
 
   const proxy = Object.create(Object.getPrototypeOf(target))
-  def(target, existingFlag, proxy)
+  
+  // skip frozen object
+  if (Object.isExtensible(target)) {
+    def(target, existingFlag, proxy)
+  }
 
   def(proxy, ReactiveFlags.IS_READONLY, true)
   def(proxy, ReactiveFlags.RAW, target)