diff --git a/src/index.ts b/src/index.ts
index ba40f130..a5036dd5 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -31,7 +31,7 @@ const defaultKeyStoreInitializer = (c: Context): KeyStorer => {
 
 export const verifyFirebaseAuth = (
   userConfig: VerifyFirebaseAuthConfig
-): Handler<string, VerifyFirebaseAuthEnv> => {
+): Handler => {
   const config = {
     projectId: userConfig.projectId,
     AuthorizationHeaderKey:
diff --git a/test/index.test.ts b/test/index.test.ts
index a69751c9..fc6eb0d6 100644
--- a/test/index.test.ts
+++ b/test/index.test.ts
@@ -32,7 +32,7 @@ describe("verifyFirebaseAuth middleware", () => {
 
   describe("service worker syntax", () => {
     test("valid case, should be 200", async () => {
-      const app = new Hono<VerifyFirebaseAuthEnv>();
+      const app = new Hono();
 
       resetAuth();