diff --git a/Build.md b/Build.md
index 52c247b..3580109 100644
--- a/Build.md
+++ b/Build.md
@@ -8,11 +8,6 @@ See [[Getting-started]] for recommended configuration options for common systems
 
 You may append `-G Ninja -DCMAKE_CXX_LINK_FLAGS=-fuse-ld=lld -DCMAKE_CXX_COMPILER=clang++`
 
-[**Windows**] On Windows you have to explicitly tell CMake to target 64-bit
-architecture by adding the `-DCMAKE_GENERATOR_PLATFORM=x64` option to the
-cmake invocation (`cmake -DCMAKE_GENERATOR_PLATFORM=x64 ..`). 32-bit builds 
-are not supported at the moment.
-
 ## CMake Options
 
 * `-DCMAKE_BUILD_TYPE=(Debug|MinSizeRel|Release|RelWithDebInfo)`
@@ -80,7 +75,22 @@ Build ccls with `/usr/bin/clang++`. You may use the absolute path of `Release/cl
 
 ## Windows
 
-If using Windows the automatically downloaded LLVM binaries are 64-bit; you should build ccls in 64-bit as well. You can tell cmake to build 64-bit using `-DCMAKE_GENERATOR_PLATFORM=x64`
+The Windows archive on releases.llvm.org does not contain library headers, since ccls uses Clang C++ APIs, it is not possible to build ccls with these releases. You have to either:
+
+1. Build LLVM+Clang by yourself with your favorite toolchain.
+2. Get prebuilt LLVM+Clang from other sources.
+
+For 2, one possible way is use MSYS2, in MSYS2 MinGW 64-bit shell:
+
+```
+pacman -S mingw-w64-x86_64-clang mingw-w64-x86_64-jq mingw-w64-x86_64-ninja mingw-w64-x86_64-ncurses
+mkdir build
+cd build
+cmake .. -G Ninja  -DSYSTEM_CLANG=ON
+cmake --build  .
+```
+
+Building ccls with MSVC 2017 and locally built LLVM+Clang on Windows does not work right now, contributions welcome.
 
 ## Link against clang+llvm libraries compiled from source