Directus error: foreign key constraint 'test_tes_foreign' are incompatible

Question

In Directus version 10:

I set DB_CHARSET = "utf8mb4" in the .env file but I get this error when creating fields :

"alter table test77777 add constraint test77777_test_foreign foreign key (test) references directus_files (id) on delete SET NULL - UNKNOWN_CODE_PLEASE_REPORT: Referencing column 'test' and referenced column 'id' in foreign key constraint 'test77777_test_foreign' are incompatible."

My database has the settings: charset utf8mb4 and collation utf8mb4_general_ci