For reference when reading the following: a Ruby symbol is represented in the form :symbol and is serialized to the BSON Symbol type. Using the most recent Ruby driver (1.12.0.rc0), with MongoDB server version 2.6: client = MongoClient. new db = client[ 'test' ] db.create_collection(:foo) db.drop_collection(:foo) => true This is what mongosniff shows: 127.0.0.1:56381 -->> 127.0.0.1:27017 admin.$cmd 58 bytes id:e 14 query: { drop: "foo" } ntoreturn: -1 ntoskip: 0 127.0.0.1:27017 <<-- 127.0.0.1:56381 88 bytes id:f 15 - 14 reply n:1 cursorId: 0 { ns: "admin.foo" , nIndexesWas: 1, ok: 1.0 }   With MongoDB nightly Nov-18-2014 and the most recent Ruby driver (1.12.0.rc0): client = MongoClient. new db = client[ 'test' ] db.create_collection(:foo) db.drop_collection(:foo) => false And this is the mongosniff output 127.0.0.1:56381 -->> 127.0.0.1:27017 admin.$cmd 58 bytes id:13 19 query: { drop: "foo" } ntoreturn: -1 ntoskip: 0 127.0.0.1:27017 <<-- 127.0.0.1:56381 94 bytes id:14 20 - 19 reply n:1 cursorId: 0 { ok: 0.0, errmsg: "no collection name specified" } In looking at the commit that changed this behavior, other commands are probably affected as well.