Error 127 when trying to run Zookeeper through supervisord

I'm getting (exit status 127; not expected) when I try to run Zookeeper through supervisord, and the errors I'm getting back aren't helpful. Running it as the normal user works just fine:

[ec2-user@ip-10-1-90-214 zookeeper-3.4.6]$ sudo bin/zkServer.sh start
JMX enabled by default
Using config: /home/ec2-user/zookeeper-3.4.6/bin/../conf/zoo.cfg
Starting zookeeper ... STARTED

But when running it through supervisord (with -n, so I can see the output):

[ec2-user@ip-10-1-90-214 zookeeper-3.4.6]$ supervisord -n
2015-04-20 21:51:51,834 INFO RPC interface 'supervisor' initialized
2015-04-20 21:51:51,834 CRIT Server 'unix_http_server' running without any HTTP authentication checking
2015-04-20 21:51:51,834 INFO supervisord started with pid 24004
2015-04-20 21:51:52,836 INFO spawned: 'zookeeper' with pid 24007
2015-04-20 21:51:52,841 INFO exited: zookeeper (exit status 127; not expected)

The relevant part of /etc/supervisord.conf:

[program:zookeeper]
command=/home/ec2-user/zookeeper-3.4.6/bin/zkServer.sh start -c /etc/supervisord.conf
autorestart=true
user=ec2-user

I've tried tinkering with all sorts of settings such as exitcodes and the like. Any ideas?