Error with "Read Backup" (1 reply)

I have a database with about 40 tables. I have been trying to alter the tables using the query:

ALTER TABLE <table_name> algorithm=inplace, COMMENT="NDB_TABLE=READ_BACKUP=1";

This works on some tables, but in others I get the error:

error 741 'Unsupported alter table' from NDBCLUSTER

All the tables are ndbcluster tables and I can't find any rhyme or reason about why some tables are successfully altered and some aren't. This is with cluster version 7.5.4.

Any ideas what to do?