Deadlock while doing VACUUM and DROP

Hello everyone,

I encountered deadlock during DROP TABLE statement:

2018-10-23 14:49:55 CEST psql > ERROR:  deadlock detected
2018-10-23 14:49:55 CEST psql > DETAIL:  Process 89171 waits for 
AccessExclusiveLock on relation 17582 of database 16390; blocked by 
process 50837.
         Process 50837 waits for AccessShareLock on relation 20767 of 
database 16390; blocked by process 89171.
         Process 89171: DROP TABLE IF EXISTS sm.tasks;
         Process 50837: autovacuum: ANALYZE sm.tasks


This happenend CentOS 7 with Linux kernel 3.10.0-693 using PostgreSQL 9.6.6.

There was discussion about similar issue without any conclusions 10 
years ago, I'm not sure whether it's a bug or some documented behaviour.

https://www.postgresql.org/message-id/flat/482CCD42.1060705%40students.mimuw.edu.pl


Is there anything I can do make sure that DDL statement won't be 
canceled due to collision with autovaccum?


Regards,
Michal Merta