diff --git a/CHANGES.txt b/CHANGES.txt
index e311bb79a1..43f688b59e 100644
--- a/CHANGES.txt
+++ b/CHANGES.txt
@@ -14,6 +14,7 @@ Features
 Bugfixes
 --------
 
+* Really add missing trailing slashes in ``BASE_URL`` (Issue #1651)
 * Check if files exists before adding them as post-list dependencies
   (Issue #1646)
 * Fix build command in ``nikola auto`` (Issue #1641)
diff --git a/nikola/nikola.py b/nikola/nikola.py
index d1e6faa9d6..64ab726006 100644
--- a/nikola/nikola.py
+++ b/nikola/nikola.py
@@ -616,6 +616,7 @@ def __init__(self, **config):
         # BASE_URL should *always* end in /
         if self.config['BASE_URL'] and self.config['BASE_URL'][-1] != '/':
             utils.LOGGER.warn("Your BASE_URL doesn't end in / -- adding it, but please fix it in your config file!")
+            self.config['BASE_URL'] += '/'
 
         # todo: remove in v8
         if not isinstance(self.config['DEPLOY_COMMANDS'], dict):