diff --git a/mercurial/url.py b/mercurial/url.py
--- a/mercurial/url.py
+++ b/mercurial/url.py
@@ -527,6 +527,9 @@ if has_https:
                 self.ui.debug('%s certificate successfully verified\n' %
                               self.host)
             else:
+                self.ui.warn(_("warning: %s certificate not verified "
+                               "(check web.cacerts config setting)\n") % 
+                             self.host)
                 httplib.HTTPSConnection.connect(self)
 
     class httpsconnection(BetterHTTPS):
diff --git a/tests/test-https.t b/tests/test-https.t
--- a/tests/test-https.t
+++ b/tests/test-https.t
@@ -106,6 +106,7 @@ Test server address cannot be reused
 clone via pull
 
   $ hg clone https://localhost:$HGPORT/ copy-pull
+  warning: localhost certificate not verified (check web.cacerts config setting)
   requesting all changes
   adding changesets
   adding manifests
@@ -131,6 +132,7 @@ pull
   $ echo '[hooks]' >> .hg/hgrc
   $ echo "changegroup = python '$TESTDIR'/printenv.py changegroup" >> .hg/hgrc
   $ hg pull
+  warning: localhost certificate not verified (check web.cacerts config setting)
   changegroup hook: HG_NODE=5fed3813f7f5e1824344fdc9cf8f63bb662c292d HG_SOURCE=pull HG_URL=https://localhost:$HGPORT/ 
   pulling from https://localhost:$HGPORT/
   searching for changes