diff --git a/appveyor.yml b/appveyor.yml
index ccd99e301..276b8b400 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -1,20 +1,24 @@
 # AppVeyor file
 # http://www.appveyor.com/docs/appveyor-yml
 
+# Operating system (build VM template)
+os: Previous Windows Server 2012 R2  # using previous worker images since default worker has problem installing DART-Prerequisites.msi
+
+# clone directory
+clone_folder: c:\projects\assimp
+
 # branches to build
 branches:
   # whitelist
   only:
     - master
 
-# clone directory
-clone_folder: c:\projects\assimp
-
 platform: x64
 configuration: Release
 
 build:
 
 build_script:
+- cd assimp
 - cmake -G"Visual Studio 11" ..
 - msbuild /m /p:Configuration=Release /p:Platform="Win32" Assimp.sln