diff --git a/packages/reactivity/__tests__/reactive.spec.ts b/packages/reactivity/__tests__/reactive.spec.ts
index aabd95456..a23f2066f 100644
--- a/packages/reactivity/__tests__/reactive.spec.ts
+++ b/packages/reactivity/__tests__/reactive.spec.ts
@@ -301,6 +301,13 @@ describe('reactivity/reactive', () => {
     expect(() => markRaw(obj)).not.toThrowError()
   })
 
+  test('should not markRaw object as reactive', () => {
+    const a = reactive({ a: 1 })
+    const b = reactive({ b: 2 }) as any
+    b.a = markRaw(toRaw(a))
+    expect(b.a === a).toBe(false)
+  })
+
   test('should not observe non-extensible objects', () => {
     const obj = reactive({
       foo: Object.preventExtensions({ a: 1 }),
diff --git a/packages/reactivity/src/reactive.ts b/packages/reactivity/src/reactive.ts
index 729c85496..c549d7291 100644
--- a/packages/reactivity/src/reactive.ts
+++ b/packages/reactivity/src/reactive.ts
@@ -279,16 +279,16 @@ function createReactiveObject(
   ) {
     return target
   }
-  // target already has corresponding Proxy
-  const existingProxy = proxyMap.get(target)
-  if (existingProxy) {
-    return existingProxy
-  }
   // only specific value types can be observed.
   const targetType = getTargetType(target)
   if (targetType === TargetType.INVALID) {
     return target
   }
+  // target already has corresponding Proxy
+  const existingProxy = proxyMap.get(target)
+  if (existingProxy) {
+    return existingProxy
+  }
   const proxy = new Proxy(
     target,
     targetType === TargetType.COLLECTION ? collectionHandlers : baseHandlers,