Index: trac/versioncontrol/svn_fs.py
===================================================================
--- trac/versioncontrol/svn_fs.py	(revision 6685)
+++ trac/versioncontrol/svn_fs.py	(working copy)
@@ -347,7 +347,7 @@
                 prefix.append(pref)
             href = self._externals_map.get(base_url)
             revstr = rev and ' at revision '+rev or ''
-            if not href and url.startswith('http://'):
+            if not href and (url.startswith('http://') or url.startswith('https://')):
                 href = url
             if href:
                 remotepath = posixpath.join(*reversed(prefix))