diff --git a/types/netmask/index.d.ts b/types/netmask/index.d.ts
index 694f819242..ba0a9d8697 100644
--- a/types/netmask/index.d.ts
+++ b/types/netmask/index.d.ts
@@ -2,6 +2,7 @@
 // Project: https://github.com/rs/node-netmask
 // Definitions by: Matt Frantz <https://github.com/mhfrantz>
 //                 JanST123 <https://github.com/JanST123>
+//                 Junxiao Shi <https://github.com/yoursunny>
 // Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
 
 /**
@@ -74,5 +75,5 @@ export class Netmask {
      * @param net A network - e.g 216.240.32.0/24
      * @param mask - optional netmask if not provided in `net`
      */
-    constructor(net: string, mask?: string);
+    constructor(net: string, mask?: string | number);
 }
diff --git a/types/netmask/netmask-tests.ts b/types/netmask/netmask-tests.ts
index 06a29650b2..5b770c321b 100644
--- a/types/netmask/netmask-tests.ts
+++ b/types/netmask/netmask-tests.ts
@@ -1,12 +1,15 @@
 import netmask = require('netmask');
 
-const block = new netmask.Netmask('10.0.0.0/12');
+let block = new netmask.Netmask('10.0.0.0/12');
 console.log('base', block.base);
 
 if (block.contains('10.0.8.10')) {
     console.log('block contains 10.0.8.10');
 }
 
+block = new netmask.Netmask('216.240.32.0', '255.255.255.0');
+block = new netmask.Netmask('216.240.32.0', 24);
+
 class CustomizedNetmask extends netmask.Netmask {
     // Test that we can override `next` to return a CustomizedNetmask (as opposed to netmask.Netmask) object
     next(count: number = 1): CustomizedNetmask {