diff --git a/Lib/urllib/request.py b/Lib/urllib/request.py
index cf065715..94b713e 100644
--- a/Lib/urllib/request.py
+++ b/Lib/urllib/request.py
@@ -1781,6 +1781,8 @@
             urlfile = file
             if file[:1] == '/':
                 urlfile = 'file://' + file
+            elif file[:2] == './':
+                raise ValueError("local file url may start with / or file:. Unknown url of type: %s" % url)
             return addinfourl(open(localname, 'rb'), headers, urlfile)
         raise URLError('local file error', 'not on local host')