inject in Authentication guard is giving me type any in angular 17

I create a functional guard in angular 17

import { Inject } from '@angular/core';

export const checkoutGuard: CanActivateFn = (route, state) => {
const customerService = Inject(CustomerService);
const router = Inject(Router);
if(customerService.isAuthenticated()) {
return true;
} else {
return router.navigateByUrl('/login');
}
};


I get the error customerService.isAuthenticated is not a function. I declared the service in app.config.ts providers: [provideRouter(routes), provideHttpClient(), CustomerService,] this what iI declared in routes {path:'checkout', component:CheckoutComponent, canActivate:[checkoutGuard]} this is the service class

@Injectable({ providedIn: 'root' })
export class CustomerService {
isAuthenticated():boolean { return true; }
}

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