diff -r e12ecb3c672f Lib/test/test_urlparse.py
--- a/Lib/test/test_urlparse.py	Sat Nov 20 11:21:20 2010 -0500
+++ b/Lib/test/test_urlparse.py	Sat Nov 20 15:19:48 2010 -0500
@@ -257,6 +257,7 @@
         self.checkJoin(RFC3986_BASE, 'g#s','http://a/b/c/g#s')
         self.checkJoin(RFC3986_BASE, 'g?y#s','http://a/b/c/g?y#s')
         self.checkJoin(RFC3986_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;x','http://a/b/c/g;x')
         self.checkJoin(RFC3986_BASE, 'g;x?y#s','http://a/b/c/g;x?y#s')
         self.checkJoin(RFC3986_BASE, '','http://a/b/c/d;p?q')
diff -r e12ecb3c672f Lib/urllib/parse.py
--- a/Lib/urllib/parse.py	Sat Nov 20 11:21:20 2010 -0500
+++ b/Lib/urllib/parse.py	Sat Nov 20 15:19:48 2010 -0500
@@ -260,14 +260,9 @@
     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))
+        params = bparams
         if not query:
             query = bquery
         return urlunparse((scheme, netloc, path,