diff --git a/utils/lit/lit/TestingConfig.py b/utils/lit/lit/TestingConfig.py
index 0d9bc00a835..c7a03dd9b7b 100644
--- a/utils/lit/lit/TestingConfig.py
+++ b/utils/lit/lit/TestingConfig.py
@@ -18,6 +18,7 @@ class TestingConfig:
                 'SYSTEMROOT' : os.environ.get('SYSTEMROOT',''),
                 'LLVM_DISABLE_CRT_DEBUG' : '1',
                 'PRINTF_EXPONENT_DIGITS' : '2',
+                'PYTHONUNBUFFERED' : '1',
                 }
 
             config = TestingConfig(parent,