diff --git a/Lib/test/support/os_helper.py b/Lib/test/support/os_helper.py
index 2c45fe2369ec36b..daf6060940e97f0 100644
--- a/Lib/test/support/os_helper.py
+++ b/Lib/test/support/os_helper.py
@@ -467,12 +467,23 @@ def _rmtree(path):
 
         def _rmtree_inner(path):
             from test.support import _force_run
+            # Clear file flags (e.g. UF_IMMUTABLE, UF_NOUNLINK on BSD).
+            if hasattr(os, 'chflags'):
+                try:
+                    os.chflags(path, 0)
+                except OSError:
+                    pass
             for name in _force_run(path, os.listdir, path):
                 fullname = os.path.join(path, name)
                 try:
                     mode = os.lstat(fullname).st_mode
                 except OSError:
                     mode = 0
+                if hasattr(os, 'lchflags'):
+                    try:
+                        os.lchflags(fullname, 0)
+                    except OSError:
+                        pass
                 if stat.S_ISDIR(mode):
                     _rmtree_inner(fullname)
                     _force_run(path, os.rmdir, fullname)