Spec tests for the GridFS spec have been updated to no longer include the deprecated md5 , contentType , and aliases fields. The tests in question don't assert driver behaviour but only include values in the initial documents, which are then re-used in outcome assertions. Additionally, a test verifying that a contentType provided during an upload operation is correctly stored in the document. If your driver still supports this deprecated field, you will want to keep this particular test around until the behaviour is removed. To update, sync the gridfs spec tests to commit 12be2dfab99bdad54c3499174b0519ddb4588332 .