diff --git a/lib/luvit/fs.lua b/lib/luvit/fs.lua
index d78917ccf..9d4a139f3 100644
--- a/lib/luvit/fs.lua
+++ b/lib/luvit/fs.lua
@@ -33,7 +33,6 @@ local sizes = {
   Rename = 2,
   Fsync = 1,
   Fdatasync = 1,
-  Ftruncate = 2,
   Sendfile = 4,
   Chmod = 2,
   Utime = 3,
@@ -177,6 +176,43 @@ function fs.appendFileSync(path, data)
   fs.closeSync(fd)
 end
 
+function fs.ftruncate(fd, len, callback)
+  if callback == nil then
+    callback = len
+    len = nil
+  end
+  native.fsFtruncate(fd, len or 0, callback or default)
+end
+
+function fs.ftruncateSync(fd, len)
+  return native.fsFtruncate(fd, len or 0)
+end
+
+function fs.truncate(path, len, callback)
+  if callback == nil then
+    callback = len
+    len = nil
+  end
+  fs.open(path, 'w', function(err, fd)
+    if err then return callback(err) end
+    native.fsFtruncate(fd, len or 0, function(err)
+      fs.close(fd, function(err2)
+        (callback or default)(err or err2)
+      end)
+    end)
+  end)
+end
+
+function fs.truncateSync(path, len)
+  local fd = fs.openSync(path, 'w')
+  local ok, err
+  ok, err = pcall(native.fsFtruncate, fd, len or 0)
+  if not ok then
+    return err
+  end
+  fs.closeSync(fd)
+end
+
 local CHUNK_SIZE = 65536
 
 local read_options = {
diff --git a/tests/test-fs-truncate.lua b/tests/test-fs-truncate.lua
new file mode 100644
index 000000000..7dcb1e12b
--- /dev/null
+++ b/tests/test-fs-truncate.lua
@@ -0,0 +1,133 @@
+--[[
+
+Copyright 2012 The Luvit Authors. All Rights Reserved.
+
+Licensed under the Apache License, Version 2.0 (the "License")
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS-IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+
+--]]
+
+require("helper")
+
+local FS = require('fs')
+local Path = require('path')
+local Buffer = require('buffer').Buffer
+local string = require('string')
+
+local filename = Path.join(__dirname, 'tmp', 'truncate-file.txt')
+local data = string.rep('x', 1024 * 16)
+
+local stat
+
+-- truncateSync
+FS.writeFileSync(filename, data)
+stat = FS.statSync(filename)
+assert(stat.size == 1024 * 16)
+
+FS.truncateSync(filename, 1024)
+stat = FS.statSync(filename)
+assert(stat.size == 1024)
+
+FS.truncateSync(filename)
+stat = FS.statSync(filename)
+assert(stat.size == 0)
+
+-- ftruncateSync
+FS.writeFileSync(filename, data)
+local fd = FS.openSync(filename, 'a')
+
+stat = FS.statSync(filename)
+assert(stat.size == 1024 * 16)
+
+FS.ftruncateSync(fd, 1024)
+stat = FS.statSync(filename)
+assert(stat.size == 1024)
+
+FS.ftruncateSync(fd)
+stat = FS.statSync(filename)
+assert(stat.size == 0)
+
+FS.closeSync(fd)
+
+function testTruncate(cb)
+  FS.writeFile(filename, data, function(er)
+    if er then return cb(er) end
+    FS.stat(filename, function(er, stat)
+      if er then return cb(er) end
+      assert(stat.size == 1024 * 16)
+
+      FS.truncate(filename, 1024, function(er)
+        if er then return cb(er) end
+        FS.stat(filename, function(er, stat)
+          if er then return cb(er) end
+          assert(stat.size == 1024)
+
+          FS.truncate(filename, function(er)
+            if er then return cb(er) end
+            FS.stat(filename, function(er, stat)
+              if er then return cb(er) end
+              assert(stat.size == 0)
+              cb()
+            end)
+          end)
+        end)
+      end)
+    end)
+  end)
+end
+
+
+function testFtruncate(cb)
+  FS.writeFile(filename, data, function(er)
+    if er then return cb(er) end
+    FS.stat(filename, function(er, stat)
+      if er then return cb(er) end
+      assert(stat.size == 1024 * 16)
+
+      FS.open(filename, 'w', function(er, fd)
+        if er then return cb(er) end
+        FS.ftruncate(fd, 1024, function(er)
+          if er then return cb(er) end
+          FS.stat(filename, function(er, stat)
+            if er then return cb(er) end
+            assert(stat.size == 1024)
+
+            FS.ftruncate(fd, function(er)
+              if er then return cb(er) end
+              FS.stat(filename, function(er, stat)
+                if er then return cb(er) end
+                assert(stat.size == 0)
+                FS.close(fd, cb)
+              end)
+            end)
+          end)
+        end)
+      end)
+    end)
+  end)
+end
+
+-- async tests
+local success = 0
+testTruncate(function(er)
+  if er then return er end
+  success = success + 1
+  testFtruncate(function(er)
+    if er then return er end
+    success = success + 1
+  end)
+end)
+
+process:on('exit', function()
+  assert(success == 2)
+  p('ok')
+end)