diff --git a/appveyor.yml b/appveyor.yml
index 9f0efebb..5aa896ac 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -45,10 +45,10 @@ init:
 - set arch=
 - if "%PLATFORM%"=="x64" (set arch= Win64)
 - echo %APPVEYOR_BUILD_WORKER_IMAGE%
-- if "%APPVEYOR_BUILD_WORKER_IMAGE%"=="Visual Studio 2017" ( set CMAKE_GENERATOR=Visual Studio 15 2017%arch% )
-- if "%APPVEYOR_BUILD_WORKER_IMAGE%"=="Visual Studio 2015" ( set CMAKE_GENERATOR=Visual Studio 14 2015%arch% )
-- if "%APPVEYOR_BUILD_WORKER_IMAGE%"=="Visual Studio 2013" ( set CMAKE_GENERATOR=Visual Studio 12 2013%arch% )
-- if not "%MINGW_VERSION%"==[""] ( set CMAKE_GENERATOR=MinGW Makefiles )
+- if "%APPVEYOR_BUILD_WORKER_IMAGE%"=="Visual Studio 2017" (set CMAKE_GENERATOR=Visual Studio 15 2017%arch%)
+- if "%APPVEYOR_BUILD_WORKER_IMAGE%"=="Visual Studio 2015" (set CMAKE_GENERATOR=Visual Studio 14 2015%arch%)
+- if "%APPVEYOR_BUILD_WORKER_IMAGE%"=="Visual Studio 2013" (set CMAKE_GENERATOR=Visual Studio 12 2013%arch%)
+- if DEFINED MINGW_VERSION ( set CMAKE_GENERATOR=MinGW Makefiles)
 - echo "%CMAKE_GENERATOR%"
 
 before_build: