diff --git a/erb/v1/cpp03_zone.hpp.erb b/erb/v1/cpp03_zone.hpp.erb
index 7dfc35c0..dd873a69 100644
--- a/erb/v1/cpp03_zone.hpp.erb
+++ b/erb/v1/cpp03_zone.hpp.erb
@@ -10,8 +10,17 @@
 #ifndef MSGPACK_V1_CPP03_ZONE_HPP
 #define MSGPACK_V1_CPP03_ZONE_HPP
 
+#include "msgpack/versioning.hpp"
+#include "msgpack/cpp_config.hpp"
 #include "msgpack/zone_decl.hpp"
 
+#include <stdint.h>
+#include <cstdlib>
+#include <memory>
+#include <vector>
+
+#include <boost/assert.hpp>
+
 <% GENERATION_LIMIT = 15 %>
 namespace msgpack {
 
@@ -192,10 +201,11 @@ inline zone::zone(size_t chunk_size) /* throw() */ :m_chunk_size(chunk_size), m_
 
 inline char* zone::get_aligned(char* ptr, size_t align)
 {
+    BOOST_ASSERT(align != 0 && (align & (align - 1)) == 0); // align must be 2^n (n >= 0)
     return
         reinterpret_cast<char*>(
-            reinterpret_cast<size_t>(
-            (ptr + (align - 1))) / align * align);
+            reinterpret_cast<uintptr_t>(ptr + (align - 1)) & ~static_cast<uintptr_t>(align - 1)
+        );
 }
 
 inline void* zone::allocate_align(size_t size, size_t align)
diff --git a/include/msgpack/sysdep.hpp b/include/msgpack/sysdep.hpp
index 9f95b60b..ec71dead 100644
--- a/include/msgpack/sysdep.hpp
+++ b/include/msgpack/sysdep.hpp
@@ -26,6 +26,13 @@
     typedef unsigned __int32 uint32_t;
     typedef signed __int64 int64_t;
     typedef unsigned __int64 uint64_t;
+#   if defined(_WIN64)
+        typedef signed __int64 intptr_t;
+        typedef unsigned __int64 uintptr_t;
+#   else
+        typedef signed __int32 intptr_t;
+        typedef unsigned __int32 uintptr_t;
+#   endif
 #elif defined(_MSC_VER)  // && _MSC_VER >= 1600
 #   include <stdint.h>
 #else
diff --git a/include/msgpack/v1/detail/cpp03_zone.hpp b/include/msgpack/v1/detail/cpp03_zone.hpp
index 21b3c5e8..09d78be0 100644
--- a/include/msgpack/v1/detail/cpp03_zone.hpp
+++ b/include/msgpack/v1/detail/cpp03_zone.hpp
@@ -10,8 +10,17 @@
 #ifndef MSGPACK_V1_CPP03_ZONE_HPP
 #define MSGPACK_V1_CPP03_ZONE_HPP
 
+#include "msgpack/versioning.hpp"
+#include "msgpack/cpp_config.hpp"
 #include "msgpack/zone_decl.hpp"
 
+#include <stdint.h>
+#include <cstdlib>
+#include <memory>
+#include <vector>
+
+#include <boost/assert.hpp>
+
 
 namespace msgpack {
 
@@ -237,10 +246,11 @@ inline zone::zone(size_t chunk_size) /* throw() */ :m_chunk_size(chunk_size), m_
 
 inline char* zone::get_aligned(char* ptr, size_t align)
 {
+    BOOST_ASSERT(align != 0 && (align & (align - 1)) == 0); // align must be 2^n (n >= 0)
     return
         reinterpret_cast<char*>(
-            reinterpret_cast<size_t>(
-            (ptr + (align - 1))) / align * align);
+            reinterpret_cast<uintptr_t>(ptr + (align - 1)) & ~static_cast<uintptr_t>(align - 1)
+        );
 }
 
 inline void* zone::allocate_align(size_t size, size_t align)
diff --git a/include/msgpack/v1/detail/cpp11_zone.hpp b/include/msgpack/v1/detail/cpp11_zone.hpp
index c3cf3f6b..df744e31 100644
--- a/include/msgpack/v1/detail/cpp11_zone.hpp
+++ b/include/msgpack/v1/detail/cpp11_zone.hpp
@@ -14,10 +14,13 @@
 #include "msgpack/cpp_config.hpp"
 #include "msgpack/zone_decl.hpp"
 
+#include <cstdint>
 #include <cstdlib>
 #include <memory>
 #include <vector>
 
+#include <boost/assert.hpp>
+
 namespace msgpack {
 
 /// @cond
@@ -230,10 +233,11 @@ inline zone::zone(size_t chunk_size) noexcept:m_chunk_size(chunk_size), m_chunk_
 
 inline char* zone::get_aligned(char* ptr, size_t align)
 {
+    BOOST_ASSERT(align != 0 && (align & (align - 1)) == 0); // align must be 2^n (n >= 0)
     return
         reinterpret_cast<char*>(
-            reinterpret_cast<size_t>(
-            (ptr + (align - 1))) / align * align);
+            reinterpret_cast<uintptr_t>(ptr + (align - 1)) & ~static_cast<uintptr_t>(align - 1)
+        );
 }
 
 inline void* zone::allocate_align(size_t size, size_t align)
diff --git a/test/zone.cpp b/test/zone.cpp
index 1ef288a2..438f69b2 100644
--- a/test/zone.cpp
+++ b/test/zone.cpp
@@ -8,7 +8,7 @@ BOOST_AUTO_TEST_CASE(allocate_align)
     msgpack::zone z;
     char* start = (char*)z.allocate_align(1);
     BOOST_CHECK_EQUAL(0ul, reinterpret_cast<std::size_t>(start) % sizeof(int));
-    for (std::size_t s = 1; s < sizeof(int); ++s) {
+    for (std::size_t s = 1; s < sizeof(int); s <<= 1) {
         z.allocate_no_align(s);
         char* buf_a = (char*)z.allocate_align(1);
         BOOST_CHECK_EQUAL(0ul, reinterpret_cast<std::size_t>(buf_a) % sizeof(int));
@@ -18,10 +18,10 @@ BOOST_AUTO_TEST_CASE(allocate_align)
 BOOST_AUTO_TEST_CASE(allocate_align_custom)
 {
     msgpack::zone z;
-    for (std::size_t align = 1; align < 64; ++align) {
+    for (std::size_t align = 1; align < 64; align <<= 1) {
         char* start = (char*)z.allocate_align(1, align);
         BOOST_CHECK_EQUAL(0ul, reinterpret_cast<std::size_t>(start) % align);
-        for (std::size_t s = 1; s < align; ++s) {
+        for (std::size_t s = 1; s < align; s <<= 1) {
             z.allocate_no_align(s);
             char* buf_a = (char*)z.allocate_align(1, align);
             BOOST_CHECK_EQUAL(0ul, reinterpret_cast<std::size_t>(buf_a) % align);