diff --git a/types/mongodb/index.d.ts b/types/mongodb/index.d.ts
index 3048da4dd4..efdf490291 100644
--- a/types/mongodb/index.d.ts
+++ b/types/mongodb/index.d.ts
@@ -487,8 +487,9 @@ export interface Collection<TSchema = Default> {
     bulkWrite(operations: Object[], options?: CollectionBluckWriteOptions): Promise<BulkWriteOpResultObject>;
     bulkWrite(operations: Object[], options: CollectionBluckWriteOptions, callback: MongoCallback<BulkWriteOpResultObject>): void;
     /** http://mongodb.github.io/node-mongodb-native/3.0/api/Collection.html#count */
+    count(callback: MongoCallback<number>): void;
     count(query: Object, callback: MongoCallback<number>): void;
-    count(query: Object, options?: MongoCountPreferences): Promise<number>;
+    count(query?: Object, options?: MongoCountPreferences): Promise<number>;
     count(query: Object, options: MongoCountPreferences, callback: MongoCallback<number>): void;
     /** http://mongodb.github.io/node-mongodb-native/3.0/api/Collection.html#createIndex */
     createIndex(fieldOrSpec: string | any, callback: MongoCallback<string>): void;
diff --git a/types/mongodb/mongodb-tests.ts b/types/mongodb/mongodb-tests.ts
index bdbddb1250..a5a27bd671 100644
--- a/types/mongodb/mongodb-tests.ts
+++ b/types/mongodb/mongodb-tests.ts
@@ -35,7 +35,29 @@ MongoClient.connect('mongodb://127.0.0.1:27017/test', options, function (err: mo
     var collection = db.collection('test_insert');
     collection.insertOne({ a: 2 }, function (err: mongodb.MongoError, docs: any) {
 
-        collection.count(function (err: mongodb.MongoError, count: any) {
+        // Intentionally omitted type annotation from 'count'.
+        // This way it requires a more accurate typedef which allows inferring that it's a number.
+        collection.count(function (err: mongodb.MongoError, count) {
+            console.log(format("count = %s", count));
+        });
+
+        collection.count().then(function (count: number) {
+            console.log(format("count = %s", count));
+        });
+
+        collection.count({ foo: 1 }, function (err: mongodb.MongoError, count: number) {
+            console.log(format("count = %s", count));
+        });
+
+        collection.count({ foo: 1 }).then(function (count: number) {
+            console.log(format("count = %s", count));
+        });
+
+        collection.count({ foo: 1 }, { limit: 10 }, function (err: mongodb.MongoError, count: number) {
+            console.log(format("count = %s", count));
+        });
+
+        collection.count({ foo: 1 }, { limit: 10 }).then(function (count: number) {
             console.log(format("count = %s", count));
         });