Upgrade to Node 14 is breaking grunt compress output

[dfenske]

compress: {
      js: {
        options: {
          mode: 'gzip'
        },
        expand: true,
        cwd: 'public/appointments/assets/dist',
        src: ['*.js'],
        dest: 'public/appointments/assets/dist'
      }
   }
}

I have this task configured in my gruntfile, which is breaking when I upgrade from Node 12.4.0 to Node 14.16.1.

• On Node 12, it works correctly. The output file is readable minified javascript.
• On Node 14, it is broken. The output file is a compressed binary file.

Can anyone help me debug this issue? Thanks!