DEL command fails with types other than string

Expected:
15:00 $ redis.cli
127.0.0.1:6379> lpush list1 a b c
(integer) 3
127.0.0.1:6379> del list1
(integer) 1
127.0.0.1:6379> lpush list1 a b c
(integer) 3
127.0.0.1:6379> sadd set1 a b c
(integer) 3
127.0.0.1:6379> del set1 list1
(integer) 2

Actual:
127.0.0.1:6379> lpush list1 a b c
(integer) 3
127.0.0.1:6379> del list1
Error: Server closed the connection
not connected> quit
✔ ~/git/resque [master|✚ 3…2]
14:55 $ redis.cli
127.0.0.1:6379> lpush list1 a b c
(integer) 3
127.0.0.1:6379> sadd set1 a b c
(integer) 3
127.0.0.1:6379> del set1 list1
(error) ERRWRONGTYPE Operation against a key holding the wrong kind of value