diff --git a/context.py b/context.py
index b86c070..f1176af 100644
--- a/context.py
+++ b/context.py
@@ -18,7 +18,7 @@ class Context(object):
         if delta == 0:
             return
         elif delta > 0:
-            self.namelines.extend([None] * delta)
+            self.namelines.extend([(None, None)] * delta)
             for i in reversed(range(p.y + 1, len(self.mode.window.buffer.lines))):
                 self.namelines[i] = self.namelines[i - delta]
             for i in range(p.y, p.y + delta):