diff --git a/cmake/TaichiCXXFlags.cmake b/cmake/TaichiCXXFlags.cmake
index 7e7725d208577..7971bc3a14178 100644
--- a/cmake/TaichiCXXFlags.cmake
+++ b/cmake/TaichiCXXFlags.cmake
@@ -59,6 +59,9 @@ if ("${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "x86_64" OR "${CMAKE_SYSTEM_PROCESSOR}"
 elseif ("${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "aarch64" OR "${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "arm64")
     set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -DTI_ARCH_ARM")
     set(ARCH "arm64")
+elseif ("${CMAKE_SYSTEM_PROCESSOR}" STREQUAL "x86")
+    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -DTI_ARCH_x86")
+    set(ARCH "x86")
 else()
     message(FATAL_ERROR "Unknown processor type ${CMAKE_SYSTEM_PROCESSOR}")
 endif()
diff --git a/taichi/common/serialization.h b/taichi/common/serialization.h
index f9c4cbfd92afd..11228e71e86bd 100644
--- a/taichi/common/serialization.h
+++ b/taichi/common/serialization.h
@@ -163,10 +163,11 @@ serialize_kv_impl(SER &ser,
   (std::is_same<typename std::remove_reference<decltype(serializer)>::type, \
                 T>())
 
+#if !defined(TI_ARCH_x86)
 static_assert(
     sizeof(std::size_t) == sizeof(uint64_t),
     "sizeof(std::size_t) should be 8. Try compiling with 64bit mode.");
-
+#endif
 template <typename T, typename S>
 struct IO {
   using implemented = std::false_type;