diff --git a/utils/lit/lit/Util.py b/utils/lit/lit/Util.py
index ad4adf2f347..5635f50baef 100644
--- a/utils/lit/lit/Util.py
+++ b/utils/lit/lit/Util.py
@@ -64,7 +64,11 @@ def which(command, paths = None):
         paths = os.defpath
 
     # Get suffixes to search.
-    pathext = os.environ.get('PATHEXT', '').split(os.pathsep)
+    # On Cygwin, 'PATHEXT' may exist but it should not be used.
+    if os.pathsep == ';':
+        pathext = os.environ.get('PATHEXT', '').split(';')
+    else:
+        pathext = ['']
 
     # Search the paths...
     for path in paths.split(os.pathsep):