diff --git a/src/index.ts b/src/index.ts
index 8a98b70..cf62f2e 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -276,18 +276,19 @@ export interface MockResponse extends MockParams {
 
 // factory
 export default function createFetchMock(vi: typeof vitest): FetchMock {
-  const isMocking = vi.fn(always(true));
-
   const originalFetch = globalThis.fetch;
-  const mockedFetch = vi.fn((input, requestInit) => {
-    if (!isMocking(input, requestInit)) {
+  
+  let fetchMockObject: FetchMockObject;
+  
+  const mockedFetch = vi.fn((input: RequestInput, requestInit?: RequestInit) => {
+    if (!fetchMockObject.isMocking(input, requestInit)) {
       return originalFetch(input, requestInit);
     }
     return buildResponse(normalizeRequest(input, requestInit), '');
   }) as FetchMock;
 
   const fetchMock: FetchMock = mockedFetch as FetchMock;
-  const fetchMockObject = new FetchMockObject(mockedFetch, originalFetch, () => fetchMock);
+  fetchMockObject = new FetchMockObject(mockedFetch, originalFetch, () => fetchMock);
 
   copyMethods(fetchMockObject, fetchMock);