Migration generator splitting composite primary keys

  relationships do
    belongs_to :resource_a, App.ResourceA, primary_key?: true, allow_nil?: false
    belongs_to :resource_b, App.ResourceB, primary_key?: true, allow_nil?: false
  end

** (Postgrex.Error) ERROR 42P16 (invalid_table_definition) multiple primary keys for table "resourcea_resourceb" are not allowed
    (ecto_sql 3.10.1) lib/ecto/adapters/sql.ex:913: Ecto.Adapters.SQL.raise_sql_call_error/1
    (elixir 1.14.4) lib/enum.ex:1658: Enum."-map/2-lists^map/1-0-"/2
    (ecto_sql 3.10.1) lib/ecto/adapters/sql.ex:1005: Ecto.Adapters.SQL.execute_ddl/4
    (ecto_sql 3.10.1) lib/ecto/migration/runner.ex:327: Ecto.Migration.Runner.log_and_execute_ddl/3
    (ecto_sql 3.10.1) lib/ecto/migration/runner.ex:117: anonymous fn/6 in Ecto.Migration.Runner.flush/0
    (elixir 1.14.4) lib/enum.ex:2468: Enum."-reduce/3-lists^foldl/2-0-"/3
    (ecto_sql 3.10.1) lib/ecto/migration/runner.ex:116: Ecto.Migration.Runner.flush/0
    (ecto_sql 3.10.1) lib/ecto/migration/runner.ex:290: Ecto.Migration.Runner.perform_operation/3
make: *** [db-migrate] Error 1