If map function string ends in a semicolon mapReduce fails silently returning no results

Create some test data: use test db.test.drop() db.test.insert({ _id : 1, x : 1 }) db.test.insert({ _id : 2, x : 2 }) db.test.insert({ _id : 3, x : 2 }) Define map and reduce functions and call mapReduce: var map = "function map() { emit(this.x, 1); }" var reduce = "function reduce(key, values) { return values.length; }"   db.test.mapReduce(map, reduce, { out : { inline : 1 } }) The result is: { "results" : [ { "_id" : 1, "value" : 1 }, { "_id" : 2, "value" : 2 } ], "timeMillis" : 12, "counts" : { "input" : 3, "emit" : 3, "reduce" : 1, "output" : 2 }, "ok" : 1 } Now add a semicolon to the end of the string for the map function: var map = "function map() { emit(this.x, 1); };"   db.test.mapReduce(map, reduce, { out : { inline : 1 } }) This time the result is: { "results" : [ ], "timeMillis" : 14, "counts" : { "input" : 3, "emit" : 0, "reduce" : 0, "output" : 0 }, "ok" : 1 } Note the empty results array and the 0 emit count.