diff --git a/src/vue/__tests__/utils.test.ts b/src/vue/__tests__/utils.test.ts
index 8430988..1ca79ba 100644
--- a/src/vue/__tests__/utils.test.ts
+++ b/src/vue/__tests__/utils.test.ts
@@ -260,5 +260,9 @@ describe("utils", () => {
         d: { e: "e" },
       });
     });
+
+    test("should unref undefined", () => {
+      expect(cloneDeepUnref(ref(undefined))).toBe(undefined);
+    });
   });
 });
diff --git a/src/vue/utils.ts b/src/vue/utils.ts
index 4223fb4..b3f8a41 100644
--- a/src/vue/utils.ts
+++ b/src/vue/utils.ts
@@ -125,7 +125,7 @@ export function cloneDeep<T>(
 ): T {
   if (customizer) {
     const result = customizer(value);
-    if (result !== undefined) {
+    if (result !== undefined || isRef(value)) {
       return result as typeof value;
     }
   }