diff --git a/lib/encoder.js b/lib/encoder.js
index f013536..33510c6 100644
--- a/lib/encoder.js
+++ b/lib/encoder.js
@@ -93,7 +93,7 @@ module.exports = function buildEncode(encodingTypes, forceFloat64) {
           buf = new Buffer(3)
           buf[0] = 0xcd
           buf.writeUInt16BE(obj, 1)
-        } else if (obj < 0xffffffff) {
+        } else if (obj <= 0xffffffff) {
           buf = new Buffer(5)
           buf[0] = 0xce
           buf.writeUInt32BE(obj, 1)
diff --git a/test/32-bits-unsigned-integers.js b/test/32-bits-unsigned-integers.js
index eaa8fa3..62606c2 100644
--- a/test/32-bits-unsigned-integers.js
+++ b/test/32-bits-unsigned-integers.js
@@ -13,6 +13,7 @@ test('encoding/decoding 32-bits big-endian unsigned integers', function(t) {
   }
 
   allNum.push(0xfffffffe)
+  allNum.push(0xffffffff)
 
   allNum.forEach(function(num) {
     t.test('encoding ' + num, function(t) {
diff --git a/test/64-bits-unsigned-integers.js b/test/64-bits-unsigned-integers.js
index 4fef71f..0b30566 100644
--- a/test/64-bits-unsigned-integers.js
+++ b/test/64-bits-unsigned-integers.js
@@ -7,7 +7,7 @@ test('encoding/decoding 64-bits big-endian unsigned integers', function(t) {
   var encoder = msgpack()
     , allNum  = []
 
-  allNum.push(0xffffffff)
+  allNum.push(0x0000000100000000)
 
   allNum.push(0xffffffffeeeee)