--- a/req.py	Mon Jun 02 12:23:18 2014 +0200
+++ b/req.py	Fri May 23 18:17:44 2014 +0200
@@ -472,12 +472,16 @@
             raise ValueError(self._('can\'t parse %(value)r (expected %(format)s)')
                              % {'value': value, 'format': format})
 
+    def _base_url(self, secure=None):
+        if secure:
+            return self.vreg.config.get('https-url') or self.vreg.config['base-url']
+        return self.vreg.config['base-url']
+
     def base_url(self, secure=None):
         """return the root url of the instance
         """
-        if secure:
-            return self.vreg.config.get('https-url') or self.vreg.config['base-url']
-        return self.vreg.config['base-url']
+        url = self._base_url(secure=secure)
+        return url if url is None else url.rstrip('/') + '/'
 
     # abstract methods to override according to the web front-end #############