diff --git a/test/parallel/test-npm-install.js b/test/parallel/test-npm-install.js
index 069465466df682..1eec5f57ad6db9 100644
--- a/test/parallel/test-npm-install.js
+++ b/test/parallel/test-npm-install.js
@@ -38,12 +38,12 @@ const pkgPath = path.join(installDir, 'package.json');
 
 fs.writeFileSync(pkgPath, pkgContent);
 
-const env = Object.assign({}, process.env, {
-  PATH: path.dirname(process.execPath),
-  NPM_CONFIG_PREFIX: path.join(npmSandbox, 'npm-prefix'),
-  NPM_CONFIG_TMP: path.join(npmSandbox, 'npm-tmp'),
-  HOME: homeDir,
-});
+const env = { ...process.env,
+              PATH: path.dirname(process.execPath),
+              NPM_CONFIG_PREFIX: path.join(npmSandbox, 'npm-prefix'),
+              NPM_CONFIG_TMP: path.join(npmSandbox, 'npm-tmp'),
+              HOME: homeDir,
+};
 
 exec(`${process.execPath} ${npmPath} install`, {
   cwd: installDir,