diff --git a/certbot-nginx/certbot_nginx/nginxparser.py b/certbot-nginx/certbot_nginx/nginxparser.py
index 000908bf2..50cd15c29 100644
--- a/certbot-nginx/certbot_nginx/nginxparser.py
+++ b/certbot-nginx/certbot_nginx/nginxparser.py
@@ -227,7 +227,8 @@ class UnspacedList(list):
 
     def insert(self, i, x):
         item, spaced_item = self._coerce(x)
-        self.spaced.insert(self._spaced_position(i), spaced_item)
+        self.spaced.insert(self._spaced_position(i) if i < len(self) else i,
+                           spaced_item)
         list.insert(self, i, item)
         self.dirty = True
 
@@ -291,9 +292,6 @@ class UnspacedList(list):
         # Normalize indexes like list[-1] etc, and save the result
         if idx < 0:
             idx = len(self) + idx
-        if idx == len(self):
-            # not an index, but the slice at the end of the list
-            return len(self.spaced)
         if not 0 <= idx < len(self):
             raise IndexError("list index out of range")
         idx0 = idx
diff --git a/certbot-nginx/certbot_nginx/tests/configurator_test.py b/certbot-nginx/certbot_nginx/tests/configurator_test.py
index 40fc1f4bf..ab320796f 100644
--- a/certbot-nginx/certbot_nginx/tests/configurator_test.py
+++ b/certbot-nginx/certbot_nginx/tests/configurator_test.py
@@ -235,7 +235,7 @@ class NginxConfiguratorTest(util.NginxTest):
                 ['index', 'index.html index.htm']]],
               ['listen', '5001 ssl'],
               ['ssl_certificate', '/etc/nginx/fullchain.pem'],
-              ['ssl_certificate_key', '/etc/nginx/key.pem']]+
+              ['ssl_certificate_key', '/etc/nginx/key.pem']] +
              util.filter_comments(self.config.parser.loc["ssl_options"])
             ],
             2))