diff --git a/lib/index.js b/lib/index.js
index a892c55..5cd0b26 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -85,14 +85,13 @@ Grid.prototype.collection = function (name) {
  */
 
 Grid.prototype.remove = function (options, callback) {
-  var _id;
+  var _id = null;
   if (options._id) {
     _id = this.tryParseObjectId(options._id) || options._id;
   }
-  if (!_id) {
-    _id = options.filename;
-  }
-  return this.mongo.GridStore.unlink(this.db, _id, options, callback);
+
+  var gridStore = new this.mongo.GridStore(this.db, _id, options.filename || null, "w", options, callback);
+  return gridStore.unlink(callback);
 }
 
 /**
@@ -103,14 +102,13 @@ Grid.prototype.remove = function (options, callback) {
  */
 
 Grid.prototype.exist = function (options, callback) {
-    var _id;
-    if (options._id) {
-        _id = this.tryParseObjectId(options._id) || options._id;
-    }
-    if (!_id) {
-        _id = options.filename;
-    }
-    return this.mongo.GridStore.exist(this.db, _id, options.root, callback);
+  var query = {};
+  if (options._id)
+    query._id = this.tryParseObjectId(options._id) || options._id;
+  if (options.filename)
+    query.filename = options.filename;
+
+  return this.mongo.GridStore.exist(this.db, query, options.root, options, callback);
 }
 
 /**