diff --git a/requests/models.py b/requests/models.py
index ff0ef019..0143b877 100644
--- a/requests/models.py
+++ b/requests/models.py
@@ -751,7 +751,7 @@ class Response(object):
                 chunk = pending + chunk
             lines = chunk.splitlines()
 
-            if lines[-1][-1] == chunk[-1]:
+            if lines and lines[-1] and chunk and lines[-1][-1] == chunk[-1]:
                 pending = lines.pop()
             else:
                 pending = None