diff --git a/llvm/utils/lit/lit/main.py b/llvm/utils/lit/lit/main.py
--- a/llvm/utils/lit/lit/main.py
+++ b/llvm/utils/lit/lit/main.py
@@ -244,9 +244,17 @@
     # the buildbot level.
     tmp_dir = None
     if 'LIT_PRESERVES_TMP' not in os.environ:
-        import tempfile
-        # z/OS linker does not support '_' in paths, so use '-'.
-        tmp_dir = tempfile.mkdtemp(prefix='lit-tmp-')
+        # z/OS linker does not support '_' in paths, so use '-' and letters.
+        if sys.platform == 'zos':
+            import random
+            import string
+            while True:
+                tmp_dir = '/tmp/lit-tmp-' + ''.join(random.choice(string.ascii_letters) for i in range(8))
+                if not os.path.exists(tmp_dir): break
+            os.makedirs(tmp_dir, mode=700)
+        else:
+            import tempfile
+            tmp_dir = tempfile.mkdtemp(prefix='lit_tmp_')
         tmp_dir_envs = {k: tmp_dir for k in ['TMP', 'TMPDIR', 'TEMP', 'TEMPDIR']}
         os.environ.update(tmp_dir_envs)
         for cfg in {t.config for t in run.tests}: