Types of property 'loadChildren' are incompatible.

[Alexander Vakhterov]

Trying to lazyLoad module, i'm got compile error caused by incopatible types.
current state:

{
        name: "lazy.**",
        url: "/lazy",
        loadChildren: "../lazy/lazy.module#LazyModule"
}

And i'm got this compilation error

Type '{ name: string; url: string; loadChildren: () => Promise<{}>; component?: undefined; }' is not assignable to type 'Ng2StateDeclaration'.
          Types of property 'loadChildren' are incompatible.
            Type '() => Promise<{}>' is not assignable to type 'NgModuleToLoad'.
              Type '() => Promise<{}>' is not assignable to type 'ModuleTypeCallback'.
                Type 'Promise<{}>' is not assignable to type 'Type<any> | Promise<Type<any>>'.
                  Type 'Promise<{}>' is not assignable to type 'Promise<Type<any>>'.
                    Type '{}' is not assignable to type 'Type<any>'.
                      Property 'apply' is missing in type '{}'.

It's not throws if i will directly insert function to loadChildrent and manual cast return type to Promise

{
        name: "lazy.**",
        url: "/lazy",
        loadChildren: function() {
            return <Promise<any>>new Promise(function (resolve, reject) {
                (require as any).ensure([], function (require: any) {
                    resolve(require('..\\lazy\\lazy.module')['LazyModule']);
                }, function(e: any) {
                    reject({ loadChunkError: true, details: e });
                });})
        }
}

How to fix this?
libraries:
ts-loader 4.5.0
typescript 3.0.1
angular-router-loader 0.8.5

UPD: one more way to fix is cast with "as" keyword
loadChildren: "../lazy/lazy.module#LazyModule" as () => Promise<any>