fieldNamed does not work for columns that refetence other tables

The documentation instructs using `Database.Beam.Schema.Tables.fieldNamed` if the default name does not match actual column name. However, if I try to use it for a column that references another table, it fails to compile with

```
• Couldn't match expected type ‘PrimaryKey
RunT
(BeamTables.FieldModification
(BeamTables.TableField DbStateT))’
with actual type ‘BeamTables.FieldModification
(BeamTables.TableField tbl0) a0’

```

Is there another function that I'm supposed to use here? If so, could it be added to the documentation? Otherwise, can such a function be added together with an IsString instance?