Webpack fileloader background

Question

somebody who can help me?i use file-loader to handle images which in sass,after compiled,the file of css is

.b {
    width: 100px;
    height: 100px;
    background: url([object Object]); 
}

before:

.b{
  width: 100px;
  height: 100px;
  background: url("../images/icon-admin.png");
}

the webpack.config below

            {
                test:/\.(png|jpg|jpeg|gif)$/,
                use:['file-loader?name=images/[name].[ext]']
            }

I looking for answer so longer,wish someone help me,thanks!