_id is never casted to id string

Is there a setting I need to use to cast _id object id into a hex string? The docs says it’s enabled by default, but I get object id instead of a string id for my queries.

No source file or test is named. Start by checking the documentation claim about the default _id casting and reproduce the query result with a MongoDB ObjectId; trace the query handling that determines whether _id is returned as an ObjectId or hex string. Done means the documented default behavior and actual query result agree, with coverage for the reported case.

Written by the indexing model from the issue text.