diff --git a/lib/server.ts b/lib/server.ts
index fee88766..0d87f785 100644
--- a/lib/server.ts
+++ b/lib/server.ts
@@ -720,6 +720,11 @@ class OutMessage extends OutgoingMessage {
         }
         this.setOption('Block2', block2)
         this.setOption('ETag', _toETag(payload))
+        const size2 = getOption(this._request.options, 'Size2')
+
+        if (size2 === 0) {
+            this.setOption('Size2', payload.length)
+        }
 
         // cache it
         if (this._request.token != null && this._request.token.length > 0) {
diff --git a/package.json b/package.json
index df6df3cb..12a45d34 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "coap",
-  "version": "1.1.0",
+  "version": "1.2.0",
   "description": "A CoAP library for node modelled after 'http'",
   "main": "dist/index.js",
   "types": "dist/index.d.ts",
diff --git a/test/blockwise.ts b/test/blockwise.ts
index 497d6da8..b14d035a 100644
--- a/test/blockwise.ts
+++ b/test/blockwise.ts
@@ -7,7 +7,7 @@
  */
 
 import { nextPort } from './common'
-import { createServer, request } from '../index'
+import { createServer, IncomingMessage, request } from '../index'
 import { generate, Packet, parse } from 'coap-packet'
 import { getOption, parseBlock2 } from '../lib/helpers'
 import { generateBlockOption, parseBlockOption, exponentToByteSize, byteSizeToExponent } from '../lib/block'
@@ -363,6 +363,22 @@ describe('blockwise2', function () {
 
         parallelBlock2Test(done, checkNothing, checkBlock2Payload, checkNormalRespPayload)
     })
+
+    it.only('should support the Size2 option', function (done) {
+        request({
+            port
+        })
+            .setOption('Size2', 0)
+            .on('response', (res: IncomingMessage) => {
+                const size2 = res.headers.Size2
+                expect(size2).to.eql(payload.length)
+                setImmediate(done)
+            })
+            .end()
+        server.on('request', (req, res) => {
+            res.end(payload)
+        })
+    })
 })
 
 describe('blockwise1', () => {