diff --git a/python/cmdtest.py b/python/cmdtest.py
index 04a46a6..8d3c5d0 100755
--- a/python/cmdtest.py
+++ b/python/cmdtest.py
@@ -316,12 +316,12 @@ class TestCase:
         pass
 
     def prepend_path(self, dirpath):
-        os.environ['PATH'] = ':'.join((os.path.join(ORIG_CWD, dirpath),
-                                       os.environ['PATH']))
+        os.environ['PATH'] = os.pathsep.join((os.path.join(ORIG_CWD, dirpath),
+                                              os.environ['PATH']))
 
     def prepend_local_path(self, dirpath):
-        os.environ['PATH'] = ':'.join((os.path.join(self.__tmpdir.top, dirpath),
-                                       os.environ['PATH']))
+        os.environ['PATH'] = os.pathsep.join((os.path.join(self.__tmpdir.top, dirpath),
+                                              os.environ['PATH']))
 
     def import_file(self, src, tgt):
         mkdir_for(tgt)