diff --git a/appveyor.yml b/appveyor.yml
index f26904f4d..4bc27edfe 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -78,7 +78,7 @@ install:
   # pip will build them from source using the MSVC compiler matching the
   # target Python version and architecture
   - "%CMD_IN_ENV% pip install -r dev-requirements.txt"
-  - "%CMD_IN_ENV% python -c \"import os,subprocess,sys; os.environ.get('UIA_SUPPORT')=='YES' and sys.stdout.write(subprocess.check_output(['pip','install','comtypes'],shell=True))\""
+  - "%CMD_IN_ENV% python -c \"import os,subprocess; os.environ.get('UIA_SUPPORT')=='YES' and subprocess.check_output(['pip','install','comtypes'])\""
 
   # Enable desktop (for correct screenshots).
   #- ps: iex ((new-object net.webclient).DownloadString('https://raw.githubusercontent.com/appveyor/ci/master/scripts/enable-desktop.ps1'))