diff --git a/test/simple/test-child-process-spawnsync-env.js b/test/simple/test-child-process-spawnsync-env.js
index 0cde9ffeef..194be8f2fe 100644
--- a/test/simple/test-child-process-spawnsync-env.js
+++ b/test/simple/test-child-process-spawnsync-env.js
@@ -22,13 +22,14 @@
 var common = require('../common');
 var assert = require('assert');
 var cp = require('child_process');
+var util = require('util');
 
 if (process.argv[2] === 'child') {
   console.log(process.env.foo);
 } else {
   var expected = 'bar';
   var child = cp.spawnSync(process.execPath, [__filename, 'child'], {
-    env: {foo: expected}
+    env: util._extend(process.env, {foo: expected})
   });
 
   assert.equal(child.stdout.toString().trim(), expected);
diff --git a/test/simple/test-fs-readfile-error.js b/test/simple/test-fs-readfile-error.js
index 72e1e2e7fb..67034cd87d 100644
--- a/test/simple/test-fs-readfile-error.js
+++ b/test/simple/test-fs-readfile-error.js
@@ -23,13 +23,14 @@ var common = require('../common');
 var assert = require('assert');
 var exec = require('child_process').exec;
 var path = require('path');
+var util = require('util');
 
 var callbacks = 0;
 
 function test(env, cb) {
   var filename = path.join(common.fixturesDir, 'test-fs-readfile-error.js');
   var execPath = process.execPath + ' ' + filename;
-  var options = { env: env || {} };
+  var options = { env: util._extend(process.env, env || {}) };
   exec(execPath, options, function(err, stdout, stderr) {
     assert(err);
     assert.equal(stdout, '');
diff --git a/test/simple/test-net-GH-5504.js b/test/simple/test-net-GH-5504.js
index 0e87c8210e..e135581e21 100644
--- a/test/simple/test-net-GH-5504.js
+++ b/test/simple/test-net-GH-5504.js
@@ -21,6 +21,7 @@
 
 var common = require('../common');
 var assert = require('assert');
+var util = require('util');
 
 // this test only fails with CentOS 6.3 using kernel version 2.6.32
 // On other linuxes and darwin, the `read` call gets an ECONNRESET in
@@ -74,10 +75,10 @@ function parent() {
   var clientExited = false;
   var serverListened = false;
   var opt = {
-    env: {
+    env: util._extend(process.env, {
       NODE_DEBUG: 'net',
       NODE_COMMON_PORT: process.env.NODE_COMMON_PORT,
-    }
+    })
   };
 
   process.on('exit', function() {
diff --git a/test/simple/test-stdin-script-child.js b/test/simple/test-stdin-script-child.js
index e940c3c3f3..50af591a4e 100644
--- a/test/simple/test-stdin-script-child.js
+++ b/test/simple/test-stdin-script-child.js
@@ -21,12 +21,13 @@
 
 var common = require('../common');
 var assert = require('assert');
+var util = require('util');
 
 var spawn = require('child_process').spawn;
 var child = spawn(process.execPath, [], {
-  env: {
+  env: util._extend(process.env, {
     NODE_DEBUG: process.argv[2]
-  }
+  })
 });
 var wanted = child.pid + '\n';
 var found = '';
diff --git a/test/simple/test-util-debug.js b/test/simple/test-util-debug.js
index 6d9c28a95a..896e46f2c0 100644
--- a/test/simple/test-util-debug.js
+++ b/test/simple/test-util-debug.js
@@ -21,6 +21,7 @@
 
 var common = require('../common');
 var assert = require('assert');
+var util = require('util');
 
 if (process.argv[2] === 'child')
   child();
@@ -47,7 +48,7 @@ function test(environ, shouldWrite) {
 
   var spawn = require('child_process').spawn;
   var child = spawn(process.execPath, [__filename, 'child'], {
-    env: { NODE_DEBUG: environ }
+    env: util._extend(process.env, { NODE_DEBUG: environ })
   });
 
   expectErr = expectErr.split('%PID%').join(child.pid);