diff --git a/tests/test.rfb.js b/tests/test.rfb.js
index 01169cad..bf12a460 100644
--- a/tests/test.rfb.js
+++ b/tests/test.rfb.js
@@ -814,10 +814,32 @@ describe('Remote Frame Buffer Protocol Client', function () {
         let client;
         beforeEach(function () {
             client = makeRFB();
-            client._supportsSetDesktopSize = true;
             client.resizeSession = true;
             container.style.width = '70px';
             container.style.height = '80px';
+
+            const incoming = [ 0x00,        // msg-type=FBU
+                               0x00,        // padding
+                               0x00, 0x01,  // number of rects = 1
+                               0x00, 0x00,  // reason = server initialized
+                               0x00, 0x00,  // status = no error
+                               0x00, 0x04,  // new width = 4
+                               0x00, 0x04,  // new height = 4
+                               0xff, 0xff,
+                               0xfe, 0xcc,  // enc = (-308) ExtendedDesktopSize
+                               0x01,        // number of screens = 1
+                               0x00, 0x00,
+                               0x00,        // padding
+                               0x78, 0x90,
+                               0xab, 0xcd,  // screen id = 0
+                               0x00, 0x00,  // screen x = 0
+                               0x00, 0x00,  // screen y = 0
+                               0x00, 0x04,  // screen width = 4
+                               0x00, 0x04,  // screen height = 4
+                               0x12, 0x34,
+                               0x56, 0x78]; // screen flags
+            client._sock._websocket._receiveData(new Uint8Array(incoming));
+
             sinon.spy(RFB.messages, "setDesktopSize");
         });
 
@@ -833,6 +855,13 @@ describe('Remote Frame Buffer Protocol Client', function () {
         });
 
         it('should request a resize when initially connecting', function () {
+            // Create a new object that hasn't yet seen a
+            // ExtendedDesktopSize rect
+            client = makeRFB();
+            client.resizeSession = true;
+            container.style.width = '70px';
+            container.style.height = '80px';
+
             // Simple ExtendedDesktopSize FBU message
             const incoming = [ 0x00,        // msg-type=FBU
                                0x00,        // padding
@@ -846,17 +875,14 @@ describe('Remote Frame Buffer Protocol Client', function () {
                                0x01,        // number of screens = 1
                                0x00, 0x00,
                                0x00,        // padding
-                               0x00, 0x00,
-                               0x00, 0x00,  // screen id = 0
+                               0x78, 0x90,
+                               0xab, 0xcd,  // screen id = 0
                                0x00, 0x00,  // screen x = 0
                                0x00, 0x00,  // screen y = 0
                                0x00, 0x04,  // screen width = 4
                                0x00, 0x04,  // screen height = 4
-                               0x00, 0x00,
-                               0x00, 0x00]; // screen flags
-
-            // This property is indirectly used as a marker for the first update
-            client._supportsSetDesktopSize = false;
+                               0x12, 0x34,
+                               0x56, 0x78]; // screen flags
 
             // First message should trigger a resize
 
@@ -866,7 +892,7 @@ describe('Remote Frame Buffer Protocol Client', function () {
             // not the reported size from the server
             expect(RFB.messages.setDesktopSize).to.have.been.calledOnce;
             expect(RFB.messages.setDesktopSize).to.have.been.calledWith(
-                sinon.match.object, 70, 80, 0, 0);
+                sinon.match.object, 70, 80, 0x7890abcd, 0x12345678);
 
             RFB.messages.setDesktopSize.resetHistory();
 
@@ -884,7 +910,8 @@ describe('Remote Frame Buffer Protocol Client', function () {
             clock.tick(1000);
 
             expect(RFB.messages.setDesktopSize).to.have.been.calledOnce;
-            expect(RFB.messages.setDesktopSize).to.have.been.calledWith(sinon.match.object, 40, 50, 0, 0);
+            expect(RFB.messages.setDesktopSize).to.have.been.calledWith(
+                sinon.match.object, 40, 50, 0x7890abcd, 0x12345678);
         });
 
         it('should not request the same size twice', function () {
@@ -895,7 +922,7 @@ describe('Remote Frame Buffer Protocol Client', function () {
 
             expect(RFB.messages.setDesktopSize).to.have.been.calledOnce;
             expect(RFB.messages.setDesktopSize).to.have.been.calledWith(
-                sinon.match.object, 40, 50, 0, 0);
+                sinon.match.object, 40, 50, 0x7890abcd, 0x12345678);
 
             // Server responds with the requested size 40x50
             const incoming = [ 0x00, 0x00, 0x00, 0x01, 0x00, 0x01, 0x00, 0x00,
@@ -934,7 +961,8 @@ describe('Remote Frame Buffer Protocol Client', function () {
             clock.tick(200);
 
             expect(RFB.messages.setDesktopSize).to.have.been.calledOnce;
-            expect(RFB.messages.setDesktopSize).to.have.been.calledWith(sinon.match.object, 40, 50, 0, 0);
+            expect(RFB.messages.setDesktopSize).to.have.been.calledWith(
+                sinon.match.object, 40, 50, 0x7890abcd, 0x12345678);
         });
 
         it('should not resize when resize is disabled', function () {
@@ -974,9 +1002,9 @@ describe('Remote Frame Buffer Protocol Client', function () {
             // Simple ExtendedDesktopSize FBU message, new size: 100x100
             const incoming = [ 0x00, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00,
                                0x00, 0x64, 0x00, 0x64, 0xff, 0xff, 0xfe, 0xcc,
-                               0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+                               0x01, 0x00, 0x00, 0x00, 0xab, 0xab, 0xab, 0xab,
                                0x00, 0x00, 0x00, 0x00, 0x00, 0x04, 0x00, 0x04,
-                               0x00, 0x00, 0x00, 0x00 ];
+                               0x11, 0x22, 0x33, 0x44 ];
 
             // Note that this will cause the browser to display scrollbars
             // since the framebuffer is 100x100 and the container is 70x80.
@@ -996,8 +1024,8 @@ describe('Remote Frame Buffer Protocol Client', function () {
             clock.tick(1000);
 
             expect(RFB.messages.setDesktopSize).to.have.been.calledOnce;
-            expect(RFB.messages.setDesktopSize.firstCall.args[1]).to.equal(120);
-            expect(RFB.messages.setDesktopSize.firstCall.args[2]).to.equal(130);
+            expect(RFB.messages.setDesktopSize).to.have.been.calledWith(
+                sinon.match.object, 120, 130, 0xabababab, 0x11223344);
         });
     });