diff --git a/youtube_dl/jsinterp.py b/youtube_dl/jsinterp.py
index c35765702..c75cf45b9 100644
--- a/youtube_dl/jsinterp.py
+++ b/youtube_dl/jsinterp.py
@@ -416,7 +416,7 @@ class JSInterpreter(object):
                 elif member == 'splice':
                     assertion(isinstance(obj, list), 'must be applied on a list')
                     assertion(argvals, 'takes one or more arguments')
-                    index, howMany = (argvals + [len(obj)])[:2]
+                    index, howMany = map(int, (argvals + [len(obj)])[:2])
                     if index < 0:
                         index += len(obj)
                     add_items = argvals[2:]