diff --git a/types/sequelize/index.d.ts b/types/sequelize/index.d.ts
index c227e13d55..be89371b83 100644
--- a/types/sequelize/index.d.ts
+++ b/types/sequelize/index.d.ts
@@ -5747,7 +5747,7 @@ declare namespace sequelize {
         transaction(options: TransactionOptions,
             autoCallback: (t: Transaction) => PromiseLike<any>): Promise<any>;
         transaction(autoCallback: (t: Transaction) => PromiseLike<any>): Promise<any>;
-        transaction(): Promise<Transaction>;
+        transaction(options?: TransactionOptions): Promise<Transaction>;
 
         /**
          * Close all connections used by this sequelize instance, and free all references so the instance can be
diff --git a/types/sequelize/sequelize-tests.ts b/types/sequelize/sequelize-tests.ts
index 7aef602a68..830b323dcc 100644
--- a/types/sequelize/sequelize-tests.ts
+++ b/types/sequelize/sequelize-tests.ts
@@ -1626,6 +1626,18 @@ s.transaction().then( function( t ) {
 
 } );
 
+s.transaction({
+    isolationLevel: s.Transaction.ISOLATION_LEVELS.READ_COMMITTED
+    }).then(function(t2) {
+        return User.find({
+                where: {
+                    username: 'jan'
+                },
+                lock: t2.LOCK.UPDATE,
+                transaction: t2
+            });
+    });
+
 s.transaction( function() {
     return Bluebird.resolve();
 } );
diff --git a/types/sequelize/v3/index.d.ts b/types/sequelize/v3/index.d.ts
index 59c06f05bf..b0d920c32b 100644
--- a/types/sequelize/v3/index.d.ts
+++ b/types/sequelize/v3/index.d.ts
@@ -5706,7 +5706,7 @@ declare namespace sequelize {
         transaction(options: TransactionOptions,
             autoCallback: (t: Transaction) => PromiseLike<any>): Promise<any>;
         transaction(autoCallback: (t: Transaction) => PromiseLike<any>): Promise<any>;
-        transaction(): Promise<Transaction>;
+        transaction(options?: TransactionOptions): Promise<Transaction>;
 
         /**
          * Close all connections used by this sequelize instance, and free all references so the instance can be
diff --git a/types/sequelize/v3/sequelize-tests.ts b/types/sequelize/v3/sequelize-tests.ts
index 3cce75b440..8526eca809 100644
--- a/types/sequelize/v3/sequelize-tests.ts
+++ b/types/sequelize/v3/sequelize-tests.ts
@@ -1601,6 +1601,18 @@ s.transaction().then( function( t ) {
 
 } );
 
+
+s.transaction({
+    isolationLevel: s.Transaction.ISOLATION_LEVELS.READ_COMMITTED
+    }).then(function(t2) {
+        return User.find({
+                where: {
+                    username: 'jan'
+                },
+                lock: t2.LOCK.UPDATE,
+                transaction: t2
+            });
+    });
 s.transaction( function() {
     return Promise.resolve();
 } );