diff --git a/.appveyor.yml b/.appveyor.yml
index 5352e9c73d1..d4f2f74e370 100644
--- a/.appveyor.yml
+++ b/.appveyor.yml
@@ -85,6 +85,7 @@ build_script:
 test_script:
 - cd c:\pillow
 - '%PYTHON%\%PIP_DIR%\pip.exe install pytest pytest-cov'
+- c:\"Program Files (x86)"\"Windows Kits"\10\Debuggers\x86\gflags.exe /p /enable %PYTHON%\%EXECUTABLE%
 - '%PYTHON%\%EXECUTABLE% -m pytest -vx --cov PIL --cov-report term --cov-report xml Tests'
 #- '%PYTHON%\%EXECUTABLE% test-installed.py -v -s %TEST_OPTIONS%' TODO TEST_OPTIONS with pytest?