Implied $and in find query doesn't work consistently

In a mongo shell: db.doubleID.insert(_id:2,column1:2) db.doubleID.find({ $or: [ { _id: { $lte: 1.0 } }, { _id: { $lte: "1" } } ], $or: [ { _id: { $gte: 1.0 } }, { _id: { $gte: "1" } } ] }) db.doubleID.find({ $or: [ { _id: { $gte: 1.0 } }, { _id: { $gte: "1" } } ], $or: [ { _id: { $lte: 1.0 } }, { _id: { $lte: "1" } } ] }) The first find returns 1 row, the second find returns 0 rows. Explicitly stating the $and seems to work as expected: db.doubleID.find({ $and: [ {$or: [ { _id: { $lte: 1.0 } }, { _id: { $lte: "1" } } ]}, {$or: [ { _id: { $gte: 1.0 } }, { _id: { $gte: "1" } } ]}] }) This bug is not specific to the _id column, this also returns one row: db.doubleID.find({ $or: [ { column1: { $lte: 1.0 } }, { column1: { $lte: "1" } } ], $or: [ { column1: { $gte: 1.0 } }, { column1: { $gte: "1" } } ] })