const docs = [{ "_id" : 244, "m" : { "m2" : "\u0000" }}, { "_id" : 129, "m" : { "m2" : ""}}]; const q = [{ "$group" : { "_id" : null , "a" : { "$max" : "$m.m2" }}}]; const collation = { "locale" : "zh" , "strength" : 1 }; const coll = db.coll; coll.drop() coll.insert(docs) jsTestLog(coll.aggregate(q, {collation}).toArray()) // Uses SBE: [ { "_id" : null , "a" : "" } ] jsTestLog(coll.aggregate([{$_internalInhibitOptimization: {}}, ...q], {collation}).toArray()) // Uses document source $group: [ { "_id" : null , "a" : "\u0000" } ]