diff --git a/Lib/ntpath.py b/Lib/ntpath.py
index ed8a2dd..21fadd0 100644
--- a/Lib/ntpath.py
+++ b/Lib/ntpath.py
@@ -82,6 +82,12 @@
                     path += b
                 else:
                     path += "\\" + b
+            else:
+                # path is not empty and does not end with a backslash,
+                # but b is empty; since, e.g., split('a/') produces
+                # ('a', ''), it's best if join() adds a backslash in
+                # this case.
+                path += '\\'
 
     return path
 
diff --git a/Lib/test/test_ntpath.py b/Lib/test/test_ntpath.py
index 049bbc1..98569f9 100644
--- a/Lib/test/test_ntpath.py
+++ b/Lib/test/test_ntpath.py
@@ -74,6 +74,14 @@
 tester("ntpath.join('c:/', 'd:/')", 'd:/')
 tester("ntpath.join('c:/', 'd:/a/b')", 'd:/a/b')
 
+tester("ntpath.join('')", '')
+tester("ntpath.join('', '', '', '', '')", '')
+tester("ntpath.join('a')", 'a')
+tester("ntpath.join('', 'a')", 'a')
+tester("ntpath.join('', '', '', '', 'a')", 'a')
+tester("ntpath.join('a', '')", 'a\\')
+tester("ntpath.join('a', '', '', '', '')", 'a\\')
+
 tester("ntpath.normpath('A//////././//.//B')", r'A\B')
 tester("ntpath.normpath('A/./B')", r'A\B')
 tester("ntpath.normpath('A/foo/../B')", r'A\B')