max-old-space-size not working while executing webpack command to build bundle

i have been getting javascript heap out of memory error while running webpack command to build my project
i have tried to put 4GB memory allocation to node for executing webpack

this is the configuration to run the webpack command
package.json

"scripts": {
    "build:prod": "node --max-old-space-size=4096 webpack -p --config webpack/webpack.config.prod.js"
}

i am executing npm run build:prod and when i print the allocated memory

{ total_heap_size: 6537216,
  total_heap_size_executable: 1048576,
  total_physical_size: 5222208,
  total_available_size: 1520740616,
  used_heap_size: 4015776,
  heap_size_limit: 1526909922,
  malloced_memory: 8192,
  peak_malloced_memory: 421336,
  does_zap_garbage: 0 }

it still shows 1.5GB
what am i doing wrong here, i am using below code to print above stats

const v8 = require('v8');

const heapStats = v8.getHeapStatistics();
console.log(heapStats);