diff --git a/CMakeLists.txt b/CMakeLists.txt
index cce4efe4..7db567c0 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -32,17 +32,6 @@ else()
     add_definitions(-DSEXP_USE_DL=0)
 endif()
 
-if(CMAKE_SIZEOF_VOID_P EQUAL 8)
-    if(MSVC)
-        # On MSVC, SEXP_64_BIT is not supported for now (#438)
-        add_definitions(-DSEXP_64_BIT=0)
-    else()
-        add_definitions(-DSEXP_64_BIT=1)
-    endif()
-elseif(CMAKE_SIZEOF_VOID_P EQUAL 4)
-    add_definitions(-DSEXP_64_BIT=0)
-endif()
-
 if(HAVE_STDINT_H)
     add_definitions(-DSEXP_USE_INTTYPES=1)
 endif()
diff --git a/README-win32.md b/README-win32.md
index 3b5f7d0c..969d550b 100644
--- a/README-win32.md
+++ b/README-win32.md
@@ -12,7 +12,7 @@ Supported Environments
 
 Chibi-scheme can be compiled with following platforms:
 
-* Microsoft Visual Studio 2017 (32bit only)
+* Microsoft Visual Studio 2017
 * MinGW32
 * MinGW64
 * MSYS
@@ -74,8 +74,8 @@ it does not support UNIX/APPLE platforms either.
 
 1. (Make sure CMake was selected with Visual Studio installer)
 2. Open this directory with "Open with Visual Studio"
-3. Choose "x86-Release" or "x86-Debug" configuration
+3. Choose "x86-" or "x64-" configuration
 4. "CMake" => "Build all"
-5. "CMake" => "Run Tests" => "chibi-scheme"
+5. "CMake" => "Tests" => "Run chibi-scheme Tests"
 
 
diff --git a/appveyor.yml b/appveyor.yml
index 22e4197a..1beb707e 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -20,11 +20,15 @@ environment:
         - ARCH: x86
           TOOLCHAIN: MSVC
           BUILDSYSTEM: CMAKE
+        - ARCH: x64
+          TOOLCHAIN: MSVC
+          BUILDSYSTEM: CMAKE
 
 install:
     - if %BUILDSYSTEM%.==CMAKE. cinst ninja
     - if %BUILDSYSTEM%.==CMAKE. set PATH=c:/tools/ninja;%PATH%
-    - if %TOOLCHAIN%.==MSVC. call "C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Auxiliary\Build\vcvars32.bat"
+    - if %TOOLCHAIN%%ARCH%.==MSVCx86. call "C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Auxiliary\Build\vcvars32.bat"
+    - if %TOOLCHAIN%%ARCH%.==MSVCx64. call "C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\VC\Auxiliary\Build\vcvars64.bat"
 
 before_build:
     - set BUILDTYPE= %ARCH%%TOOLCHAIN%
diff --git a/include/chibi/sexp.h b/include/chibi/sexp.h
index c0e83e28..1a97c683 100644
--- a/include/chibi/sexp.h
+++ b/include/chibi/sexp.h
@@ -209,10 +209,6 @@ enum sexp_types {
 #endif
 
 #ifdef _WIN32
-#if defined(_MSC_VER) && SEXP_64_BIT
-/* On SEXP_64_BIT, 128bits arithmetic is mandatory */
-#error Unsupported configuration
-#endif
 #if SEXP_64_BIT
 typedef unsigned int sexp_tag_t;
 typedef unsigned long long sexp_uint_t;