Invalid argument exception on firestore query

[OrchiDorchi]

Hi there,
I am currently working on a prjoect that needs to query firestore a lot.
My problem is that when I do this query

_firestore
.collection('users')
.where(FieldPath.documentId, whereIn: _ids)
.where('age', isGreaterThan: _preferedMinAge)
.get()
.then((value) {
for (var i = 0; i < value.docs.length; i++) {
print(value.docs[i].id);
}
});

I am getting an exception as

E/flutter ( 9184): [ERROR:flutter/lib/ui/ui_dart_state.cc(209)] Unhandled Exception: [cloud_firestore/invalid-argument] Client specified an invalid argument. Note that this differs from failed-precondition. invalid-argument indicates arguments that are problematic regardless of the state of the system (e.g., an invalid field name).
E/flutter ( 9184): #0 MethodChannelQuery.get (package:cloud_firestore_platform_interface/src/method_channel/method_channel_query.dart:110:7)
E/flutter ( 9184):
E/flutter ( 9184): #1 _JsonQuery.get (package:cloud_firestore/src/query.dart:390:9)
E/flutter ( 9184):

but I am sure that there is a 'age' field in docs. Interesting thing is,
when I do this query,

_firestore
.collection('users')
.where(FieldPath.documentId, whereIn: _ids)
.where('isPremium', isEqualTo: true)
.get()
.then((value) {
for (var i = 0; i < value.docs.length; i++) {
print(value.docs[i].id);
}
});

It succesfully does the query.
Is there anything I overlooked?