SQLServer 2016 AlwaysOn with SQL 2017 Secondary replica

   We do have SQL Server 2016 with couple of databases configured with AlwaysOn with 2 secondary replicas.  We would like to add another replica in SQL 2017 and test it with that once everything looks good, we will start using SQL 2017 and decommission the SQL2016. In case of issues, we will go back to SQL2016.

   Is this supported? SQL 2016 always on with SQL2017 as a secondary replica.  

   I remember seeing in couple of places mentioning it is possible, some places it says not possible, sql version has to be same. So got confused.

Thanks