diff --git a/lib/write-type.js b/lib/write-type.js
index 94a10ab..c76fa76 100644
--- a/lib/write-type.js
+++ b/lib/write-type.js
@@ -26,6 +26,7 @@ exports.getWriteType = getWriteType;
 function getWriteType(options) {
   var token = WriteToken.getWriteToken(options);
   var useraw = options && options.useraw;
+  var functions = options && options.functions;
   var binarraybuffer = HAS_UINT8ARRAY && options && options.binarraybuffer;
   var isBuffer = binarraybuffer ? Bufferish.isArrayBuffer : Bufferish.isBuffer;
   var bin = binarraybuffer ? bin_arraybuffer : bin_buffer;
@@ -229,6 +230,10 @@ function getWriteType(options) {
   // map 32 -- 0xdf
   function obj_to_map(encoder, value) {
     var keys = Object.keys(value);
+
+    if (!functions)
+      keys = keys.filter(function(key) { return !(value[key] instanceof Function); });
+
     var length = keys.length;
     var type = (length < 16) ? (0x80 + length) : (length <= 0xFFFF) ? 0xde : 0xdf;
     token[type](encoder, length);
diff --git a/test/28.functions.js b/test/28.functions.js
new file mode 100644
index 0000000..cf8fbd5
--- /dev/null
+++ b/test/28.functions.js
@@ -0,0 +1,26 @@
+#!/usr/bin/env mocha -R spec
+
+var assert = require("assert");
+var msgpackJS = "../index";
+var isBrowser = ("undefined" !== typeof window);
+var msgpack = isBrowser && window.msgpack || require(msgpackJS);
+var TITLE = __filename.replace(/^.*\//, "");
+var obj = {func: function() {}};
+
+describe(TITLE, function() {
+  it("functions: false", function() {
+    var options = {codec: msgpack.createCodec({functions: false})};
+
+    // as default
+    assert.deepEqual(msgpack.decode(msgpack.encode(obj)), {});
+
+    // explicit
+    assert.deepEqual(msgpack.decode(msgpack.encode(obj, options)), {});
+  });
+
+  it("functions: true", function() {
+    var options = {codec: msgpack.createCodec({functions: true})};
+
+    assert.deepEqual(msgpack.decode(msgpack.encode(obj, options)), {"func": null});
+  });
+});