sky.material.uniforms property do not exist on type Material

[tonyshare]

I am using angular9 and threejs with it's Sky model in itself example.

import { Sky } from "three/examples/jsm/objects/Sky";
...
        var sky = new Sky();
        var uniforms = sky.material.uniforms;

when I compplie the code with ng server

the compiler gave the complain:

_
: Compiled successfully.

ERROR in src/app/app.component.ts:108:37 - error TS2339: Property 'uniforms' does not exist on type 'Material | Material[]'.
  Property 'uniforms' does not exist on type 'Material'.

108         var uniforms = sky.material.uniforms;
                                        ~~~~~~~~
src/app/app.component.ts:137:26 - error TS2339: Property 'uniforms' does not exist on type 'Material | Material[]'.
  Property 'uniforms' does not exist on type 'Material'.

137             sky.material.uniforms[ 'sunPosition' ].value = light.position.copy( light.position );

_

Three.js version

"[email protected]"

Node version

v13.5.0

Angular version

Package Version

@angular-devkit/architect 0.900.0-rc.7
@angular-devkit/build-angular 0.900.0-rc.7
@angular-devkit/build-optimizer 0.900.0-rc.7
@angular-devkit/build-webpack 0.900.0-rc.7
@angular-devkit/core 9.0.0-rc.7
@angular-devkit/schematics 9.0.0-rc.7
@ngtools/webpack 9.0.0-rc.7
@schematics/angular 9.0.0-rc.7
@schematics/update 0.900.0-rc.7
rxjs 6.5.3
typescript 3.6.4
webpack 4.41.2