diff --git a/lib/cluster.js b/lib/cluster.js
index 7ca8b532ee2..ff410235b7f 100644
--- a/lib/cluster.js
+++ b/lib/cluster.js
@@ -21,5 +21,9 @@
 
 'use strict';
 
-const childOrPrimary = 'NODE_UNIQUE_ID' in process.env ? 'child' : 'primary';
+const {
+  ObjectPrototypeHasOwnProperty: ObjectHasOwn,
+} = primordials;
+
+const childOrPrimary = ObjectHasOwn(process.env, 'NODE_UNIQUE_ID') ? 'child' : 'primary';
 module.exports = require(`internal/cluster/${childOrPrimary}`);
diff --git a/test/parallel/test-cluster-basic.js b/test/parallel/test-cluster-basic.js
index e53b208ead4..306b4d7f587 100644
--- a/test/parallel/test-cluster-basic.js
+++ b/test/parallel/test-cluster-basic.js
@@ -22,13 +22,26 @@
 'use strict';
 const common = require('../common');
 
-const assert = require('assert');
-const cluster = require('cluster');
+const assert = require('node:assert');
+const cluster = require('node:cluster');
+const { spawnSync } = require('node:child_process');
 
 assert.strictEqual('NODE_UNIQUE_ID' in process.env, false,
                    `NODE_UNIQUE_ID (${process.env.NODE_UNIQUE_ID}) ` +
                    'should be removed on startup');
 
+{
+  const { status } = spawnSync(process.execPath, [
+    '-e',
+    `
+      const { strictEqual } = require('node:assert');
+      Object.setPrototypeOf(process.env, { NODE_UNIQUE_ID: 0 });
+      strictEqual(require('cluster').isPrimary, true);
+    `,
+  ]);
+  assert.strictEqual(status, 0);
+}
+
 function forEach(obj, fn) {
   Object.keys(obj).forEach((name, index) => {
     fn(obj[name], name, index);