diff --git a/lib/child_process.js b/lib/child_process.js
index e43093ace1fa0d..02d7c2344798f0 100644
--- a/lib/child_process.js
+++ b/lib/child_process.js
@@ -190,12 +190,12 @@ exports.execFile = function(file /*, args, options, callback*/) {
     // merge chunks
     var stdout;
     var stderr;
-    if (!encoding) {
-      stdout = Buffer.concat(_stdout);
-      stderr = Buffer.concat(_stderr);
-    } else {
+    if (encoding) {
       stdout = _stdout;
       stderr = _stderr;
+    } else {
+      stdout = Buffer.concat(_stdout);
+      stderr = Buffer.concat(_stderr);
     }
 
     if (ex) {
@@ -260,16 +260,16 @@ exports.execFile = function(file /*, args, options, callback*/) {
       child.stdout.setEncoding(encoding);
 
     child.stdout.addListener('data', function(chunk) {
-      stdoutLen += chunk.length;
+      stdoutLen += encoding ? Buffer.byteLength(chunk, encoding) : chunk.length;
 
       if (stdoutLen > options.maxBuffer) {
         ex = new Error('stdout maxBuffer exceeded');
         kill();
       } else {
-        if (!encoding)
-          _stdout.push(chunk);
-        else
+        if (encoding)
           _stdout += chunk;
+        else
+          _stdout.push(chunk);
       }
     });
   }
@@ -279,16 +279,16 @@ exports.execFile = function(file /*, args, options, callback*/) {
       child.stderr.setEncoding(encoding);
 
     child.stderr.addListener('data', function(chunk) {
-      stderrLen += chunk.length;
+      stderrLen += encoding ? Buffer.byteLength(chunk, encoding) : chunk.length;
 
       if (stderrLen > options.maxBuffer) {
         ex = new Error('stderr maxBuffer exceeded');
         kill();
       } else {
-        if (!encoding)
-          _stderr.push(chunk);
-        else
+        if (encoding)
           _stderr += chunk;
+        else
+          _stderr.push(chunk);
       }
     });
   }
diff --git a/test/known_issues/test-child-process-max-buffer.js b/test/known_issues/test-child-process-max-buffer.js
deleted file mode 100644
index 14a344c7062a5a..00000000000000
--- a/test/known_issues/test-child-process-max-buffer.js
+++ /dev/null
@@ -1,16 +0,0 @@
-'use strict';
-// Refs: https://github.com/nodejs/node/issues/1901
-const common = require('../common');
-const assert = require('assert');
-const cp = require('child_process');
-const unicode = '中文测试'; // Length = 4, Byte length = 13
-
-if (process.argv[2] === 'child') {
-  console.log(unicode);
-} else {
-  const cmd = `${process.execPath} ${__filename} child`;
-
-  cp.exec(cmd, { maxBuffer: 10 }, common.mustCall((err, stdout, stderr) => {
-    assert.strictEqual(err.message, 'stdout maxBuffer exceeded');
-  }));
-}
diff --git a/test/parallel/test-child-process-exec-maxBuffer.js b/test/parallel/test-child-process-exec-maxBuffer.js
new file mode 100644
index 00000000000000..714e029d728b1e
--- /dev/null
+++ b/test/parallel/test-child-process-exec-maxBuffer.js
@@ -0,0 +1,31 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const cp = require('child_process');
+
+function checkFactory(streamName) {
+  return common.mustCall((err) => {
+    const message = `${streamName} maxBuffer exceeded`;
+    assert.strictEqual(err.message, message);
+  });
+}
+
+{
+  const cmd = 'echo "hello world"';
+
+  cp.exec(cmd, { maxBuffer: 5 }, checkFactory('stdout'));
+}
+
+const unicode = '中文测试'; // length = 4, byte length = 12
+
+{
+  const cmd = `"${process.execPath}" -e "console.log('${unicode}');"`;
+
+  cp.exec(cmd, {maxBuffer: 10}, checkFactory('stdout'));
+}
+
+{
+  const cmd = `"${process.execPath}" -e "console.('${unicode}');"`;
+
+  cp.exec(cmd, {maxBuffer: 10}, checkFactory('stderr'));
+}
diff --git a/test/parallel/test-child-process-exec-stdout-data-string.js b/test/parallel/test-child-process-exec-stdout-stderr-data-string.js
similarity index 51%
rename from test/parallel/test-child-process-exec-stdout-data-string.js
rename to test/parallel/test-child-process-exec-stdout-stderr-data-string.js
index b267ff5e98347a..8ab834c98f8d79 100644
--- a/test/parallel/test-child-process-exec-stdout-data-string.js
+++ b/test/parallel/test-child-process-exec-stdout-stderr-data-string.js
@@ -4,13 +4,20 @@ const common = require('../common');
 const assert = require('assert');
 const exec = require('child_process').exec;
 
-const expectedCalls = 2;
-
-const cb = common.mustCall((data) => {
-  assert.strictEqual(typeof data, 'string');
-}, expectedCalls);
+var stdoutCalls = 0;
+var stderrCalls = 0;
 
 const command = common.isWindows ? 'dir' : 'ls';
-exec(command).stdout.on('data', cb);
+exec(command).stdout.on('data', (data) => {
+  stdoutCalls += 1;
+});
+
+exec('fhqwhgads').stderr.on('data', (data) => {
+  assert.strictEqual(typeof data, 'string');
+  stderrCalls += 1;
+});
 
-exec('fhqwhgads').stderr.on('data', cb);
+process.on('exit', () => {
+  assert(stdoutCalls > 0);
+  assert(stderrCalls > 0);
+});
diff --git a/test/parallel/test-exec-max-buffer.js b/test/parallel/test-exec-max-buffer.js
deleted file mode 100644
index 15c6e7025978e2..00000000000000
--- a/test/parallel/test-exec-max-buffer.js
+++ /dev/null
@@ -1,11 +0,0 @@
-'use strict';
-require('../common');
-var exec = require('child_process').exec;
-var assert = require('assert');
-
-var cmd = 'echo "hello world"';
-
-exec(cmd, { maxBuffer: 5 }, function(err, stdout, stderr) {
-  assert.ok(err);
-  assert.ok(/maxBuffer/.test(err.message));
-});