diff --git a/Lib/tempfile.py b/Lib/tempfile.py
--- a/Lib/tempfile.py
+++ b/Lib/tempfile.py
@@ -146,7 +146,7 @@
 
     for dir in dirlist:
         if dir != _os.curdir:
-            dir = _os.path.normcase(_os.path.abspath(dir))
+            dir = _os.path.abspath(dir)
         # Try only a few names per directory.
         for seq in range(100):
             name = next(namer)