diff --git a/lib/fs.js b/lib/fs.js
index 222efd1af6..2cc9431e45 100644
--- a/lib/fs.js
+++ b/lib/fs.js
@@ -556,7 +556,7 @@ fs.truncate = function(path, len, callback) {
     len = 0;
   }
   callback = maybeCallback(callback);
-  fs.open(path, 'w', function(er, fd) {
+  fs.open(path, 'r+', function(er, fd) {
     if (er) return callback(er);
     binding.ftruncate(fd, len, function(er) {
       fs.close(fd, function(er2) {
@@ -575,7 +575,7 @@ fs.truncateSync = function(path, len) {
     len = 0;
   }
   // allow error to be thrown, but still close fd.
-  var fd = fs.openSync(path, 'w');
+  var fd = fs.openSync(path, 'r+');
   try {
     var ret = fs.ftruncateSync(fd, len);
   } finally {
diff --git a/test/simple/test-fs-truncate-GH-6233.js b/test/simple/test-fs-truncate-GH-6233.js
new file mode 100644
index 0000000000..472afdcab9
--- /dev/null
+++ b/test/simple/test-fs-truncate-GH-6233.js
@@ -0,0 +1,44 @@
+// Copyright Joyent, Inc. and other Node contributors.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the
+// "Software"), to deal in the Software without restriction, including
+// without limitation the rights to use, copy, modify, merge, publish,
+// distribute, sublicense, and/or sell copies of the Software, and to permit
+// persons to whom the Software is furnished to do so, subject to the
+// following conditions:
+//
+// The above copyright notice and this permission notice shall be included
+// in all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
+// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
+// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
+// USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+var common = require('../common');
+var assert = require('assert');
+var fs = require('fs');
+
+var filename = common.tmpDir + '/truncate-file.txt';
+
+// Synchronous test.
+(function() {
+  fs.writeFileSync(filename, '0123456789');
+  assert.equal(fs.readFileSync(filename).toString(), '0123456789');
+  fs.truncateSync(filename, 5);
+  assert.equal(fs.readFileSync(filename).toString(), '01234');
+})();
+
+// Asynchronous test.
+(function() {
+  fs.writeFileSync(filename, '0123456789');
+  assert.equal(fs.readFileSync(filename).toString(), '0123456789');
+  fs.truncate(filename, 5, common.mustCall(function(err) {
+    if (err) throw err;
+    assert.equal(fs.readFileSync(filename).toString(), '01234');
+  }));
+})();