diff --git a/appveyor.yml b/appveyor.yml
index e75908ae..3e31c0d9 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -27,16 +27,10 @@ max_jobs: 4
 pull_requests:
   do_not_increment_build_number: true
 
-image:
-- Visual Studio 2017
-- Visual Studio 2015
-
-platform:
-- x86
-- x64
-
 environment:
   matrix:
+  - LUA_VERSION: 5.3.4
+    LLVM_VERSION: 4.0.0
   - LUA_VERSION: 5.3.4
     MINGW_VERSION: 6.3.0
   - LUA_VERSION: 5.3.4
@@ -45,6 +39,14 @@ environment:
   - LUA_VERSION: 5.2.4
   - LUA_VERSION: 5.1.5
 
+image:
+- Visual Studio 2017
+- Visual Studio 2015
+
+platform:
+- x86
+- x64
+
 matrix:
   allow_failures:
     # oldest compiler is allowed to fail here due to esoteric bugs
@@ -88,11 +90,14 @@ init:
 - if "%APPVEYOR_BUILD_WORKER_IMAGE%"=="Visual Studio 2017" (set CMAKE_GENERATOR=Visual Studio 15 2017%arch%&&set parallelism=/maxcpucount&&set logger=/logger:"C:\Program Files\AppVeyor\BuildAgent\Appveyor.MSBuildLogger.dll")
 - if "%APPVEYOR_BUILD_WORKER_IMAGE%"=="Visual Studio 2015" (set CMAKE_GENERATOR=Visual Studio 14 2015%arch%&&set parallelism=/maxcpucount&&set logger=/logger:"C:\Program Files\AppVeyor\BuildAgent\Appveyor.MSBuildLogger.dll")
 - if "%APPVEYOR_BUILD_WORKER_IMAGE%"=="Visual Studio 2013" (set CMAKE_GENERATOR=Visual Studio 12 2013%arch%&&set parallelism=/maxcpucount&&set logger=/logger:"C:\Program Files\AppVeyor\BuildAgent\Appveyor.MSBuildLogger.dll")
-- if "%MINGW_VERSION%"=="5.3.0" (set CMAKE_GENERATOR=Ninja%%set build_type=-DCMAKE_BUILD_TYPE=Release -DCMAKE_CXX_COMPILER=g++ -DCMAKE_C_COMPILER=gcc)
-- if "%MINGW_VERSION%"=="6.3.0" (set CMAKE_GENERATOR=Ninja&&set build_type=-DCMAKE_BUILD_TYPE=Release -DCMAKE_CXX_COMPILER=g++ -DCMAKE_C_COMPILER=gcc)
+- if "%MINGW_VERSION%"=="5.3.0" (set CMAKE_GENERATOR=Ninja%%set build_type=-DCMAKE_BUILD_TYPE=Release -DCMAKE_CXX_COMPILER=g++.exe -DCMAKE_C_COMPILER=gcc.exe)
+- if "%MINGW_VERSION%"=="6.3.0" (set CMAKE_GENERATOR=Ninja&&set build_type=-DCMAKE_BUILD_TYPE=Release -DCMAKE_CXX_COMPILER=g++.exe -DCMAKE_C_COMPILER=gcc.exe)
+- if "%LLVM_VERSION%"=="4.0.0" (set CMAKE_GENERATOR=Ninja&&set build_type=-DCMAKE_BUILD_TYPE=Release -DCMAKE_CXX_COMPILER=clang-cl.exe -DCMAKE_C_COMPILER=clang-cl.exe)
 # print out useful information
 - ninja --version
 - cmake --version
+- if DEFINED LLVM_VERSION (clang-cl -v)
+- if DEFINED MINGW_VERSION (g++ --version)
 - echo cmake generator -- "%CMAKE_GENERATOR%"
 
 # We need to use CMAKE_BUILD_TYPE=Release since there are no "configuration"
@@ -101,11 +106,15 @@ init:
 before_build:
 - set python_path=C:\Python36
 - set mingw_path=
+- set llvm_path=
 - if "%MINGW_VERSION%"=="5.3.0" (set mingw_path=C:\mingw-w64\i686-5.3.0-posix-dwarf-rt_v4-rev0)
 - if "%MINGW_VERSION%"=="6.3.0" ( if "%PLATFORM%"=="x64" (set mingw_path=C:\mingw-w64\x86_64-6.3.0-posix-seh-rt_v5-rev1) else ( set mingw_path=C:\mingw-w64\i686-6.3.0-posix-dwarf-rt_v5-rev1))
+- if "%LLVM_VERSION%"=="4.0.0" (set llvm_path=C:\Program Files\LLVM\bin)
 - if "%PLATFORM%"=="x64" (set python_path=C:\Python36-x64)
 - set PATH=%python_path%;%PATH%
 - set PATH=%mingw_path%;%PATH%
+- set PATH=%llvm_path%;%PATH%
+- echo PATH=%PATH%
 - md build-sol2
 - cd build-sol2
 - cmake .. -G "%CMAKE_GENERATOR%" %build_type% -DLUA_VERSION="%LUA_VERSION%" -DBUILD_LUA=ON -DBUILD_LUA_AS_DLL=OFF -DTESTS=ON -DEXAMPLES=ON -DSINGLE=ON -DTESTS_EXAMPLES=ON -DTESTS_SINGLE=ON