diff --git a/lib/parser/serializer.js b/lib/parser/serializer.js
index ee80ba67..20fab596 100644
--- a/lib/parser/serializer.js
+++ b/lib/parser/serializer.js
@@ -711,7 +711,7 @@ function serializeInto(
         index = serializeNull(buffer, key, value, index, true);
       } else if (value === null) {
         index = serializeNull(buffer, key, value, index, true);
-      } else if (value['_bsontype'] === 'ObjectId') {
+      } else if (value['_bsontype'] === 'ObjectId' || value['_bsontype'] === 'ObjectID') {
         index = serializeObjectId(buffer, key, value, index, true);
       } else if (Buffer.isBuffer(value)) {
         index = serializeBuffer(buffer, key, value, index, true);
@@ -818,7 +818,7 @@ function serializeInto(
         index = serializeDate(buffer, key, value, index);
       } else if (value === null || (value === undefined && ignoreUndefined === false)) {
         index = serializeNull(buffer, key, value, index);
-      } else if (value['_bsontype'] === 'ObjectId') {
+      } else if (value['_bsontype'] === 'ObjectId' || value['_bsontype'] === 'ObjectID') {
         index = serializeObjectId(buffer, key, value, index);
       } else if (Buffer.isBuffer(value)) {
         index = serializeBuffer(buffer, key, value, index);
@@ -920,7 +920,7 @@ function serializeInto(
         if (ignoreUndefined === false) index = serializeNull(buffer, key, value, index);
       } else if (value === null) {
         index = serializeNull(buffer, key, value, index);
-      } else if (value['_bsontype'] === 'ObjectId') {
+      } else if (value['_bsontype'] === 'ObjectId' || value['_bsontype'] === 'ObjectID') {
         index = serializeObjectId(buffer, key, value, index);
       } else if (Buffer.isBuffer(value)) {
         index = serializeBuffer(buffer, key, value, index);