diff --git a/Lib/test/libregrtest/runtest_mp.py b/Lib/test/libregrtest/runtest_mp.py
index 9604c16..74ac4fa 100644
--- a/Lib/test/libregrtest/runtest_mp.py
+++ b/Lib/test/libregrtest/runtest_mp.py
@@ -41,7 +41,7 @@
     slaveargs = json.dumps(slaveargs)
 
     cmd = [sys.executable, *support.args_from_interpreter_flags(),
-           '-X', 'faulthandler',
+           '-u',    # Unbuffered stdout and stderr
            '-m', 'test.regrtest',
            '--slaveargs', slaveargs]
     if ns.pgo:
diff --git a/PCbuild/rt.bat b/PCbuild/rt.bat
index 7d4d071..bb89f91 100644
--- a/PCbuild/rt.bat
+++ b/PCbuild/rt.bat
@@ -42,7 +42,7 @@
 if NOT "%1"=="" (set regrtestargs=%regrtestargs% %1) & shift & goto CheckOpts
 
 set exe=%prefix%python%suffix%.exe
-set cmd="%exe%" %dashO% -Wd -E -bb -m test %regrtestargs%
+set cmd="%exe%" %dashO% -u -Wd -E -bb -m test %regrtestargs%
 if defined qmode goto Qmode
 
 echo Deleting .pyc/.pyo files ...
diff --git a/Tools/scripts/run_tests.py b/Tools/scripts/run_tests.py
index b582e13..3028302 100644
--- a/Tools/scripts/run_tests.py
+++ b/Tools/scripts/run_tests.py
@@ -26,6 +26,7 @@
 
 def main(regrtest_args):
     args = [sys.executable,
+            '-u',                 # Unbuffered stdout and stderr
             '-W', 'default',      # Warnings set to 'default'
             '-bb',                # Warnings about bytes/bytearray
             '-E',                 # Ignore environment variables