diff -r 4cdd5c99c4eb Lib/test/test_urlparse.py
--- a/Lib/test/test_urlparse.py	Sat Nov 20 15:09:23 2010 -0500
+++ b/Lib/test/test_urlparse.py	Sat Nov 20 15:19:06 2010 -0500
@@ -244,6 +244,7 @@
         # Test cases from RFC3986
         self.checkJoin(RFC3986_BASE, '?y','http://a/b/c/d;p?y')
         self.checkJoin(RFC2396_BASE, ';x', 'http://a/b/c/;x')
+        self.checkJoin('http://a/b/c/de', ';x', 'http://a/b/c/;x')
         self.checkJoin(RFC3986_BASE, 'g:h','g:h')
         self.checkJoin(RFC3986_BASE, 'g','http://a/b/c/g')
         self.checkJoin(RFC3986_BASE, './g','http://a/b/c/g')
diff -r 4cdd5c99c4eb Lib/urlparse.py
--- a/Lib/urlparse.py	Sat Nov 20 15:09:23 2010 -0500
+++ b/Lib/urlparse.py	Sat Nov 20 15:19:06 2010 -0500
@@ -256,14 +256,10 @@
     if path[:1] == '/':
         return urlunparse((scheme, netloc, path,
                            params, query, fragment))
-    if not path:
+    if not path and not params:
         path = bpath
         if not params:
             params = bparams
-        else:
-            path = path[:-1]
-            return urlunparse((scheme, netloc, path,
-                                params, query, fragment))
         if not query:
             query = bquery
         return urlunparse((scheme, netloc, path,