If the default character set was set to non-latin1 then the collation order of DATA_CHAR and DATA_VARCHAR was not defined, and foreign key system tables did not work, because they contain DATA_VARCHAR columns


innobase/srv/srv0srv.c:
  If the default character set was set to non-latin1 then the collation order of DATA_CHAR and DATA_VARCHAR was not defined, and foreign key system tables did not work, because they contain DATA_VARCHAR columns