diff --git a/common/rfb/SDesktop.h b/common/rfb/SDesktop.h
index 50c92c099f..8e3388377d 100644
--- a/common/rfb/SDesktop.h
+++ b/common/rfb/SDesktop.h
@@ -89,11 +89,9 @@ namespace rfb {
 
     // setScreenLayout() requests to reconfigure the framebuffer and/or
     // the layout of screens.
-    virtual unsigned int setScreenLayout(int /*fb_width*/,
-                                         int /*fb_height*/,
-                                         const ScreenSet& /*layout*/) {
-      return resultProhibited;
-    }
+    virtual void setScreenLayout(int /*fb_width*/,
+                                 int /*fb_height*/,
+                                 const ScreenSet& /*layout*/) = 0;
 
     // frameTick() is called whenever a frame update has been processed,
     // signalling that a good time to render new data
diff --git a/common/rfb/VNCSConnectionST.cxx b/common/rfb/VNCSConnectionST.cxx
index d2bea8032a..8a21a19b26 100644
--- a/common/rfb/VNCSConnectionST.cxx
+++ b/common/rfb/VNCSConnectionST.cxx
@@ -376,6 +376,16 @@ void VNCSConnectionST::desktopReadyOrClose()
   }
 }
 
+void VNCSConnectionST::setDesktopSizeDoneOrClose(uint16_t result)
+{
+  try {
+    if (state() != RFBSTATE_NORMAL) return;
+    setDesktopSizeDone(result);
+  } catch(std::exception& e) {
+    close(e.what());
+  }
+}
+
 bool VNCSConnectionST::getComparerState()
 {
   // We interpret a low compression level as an indication that the client
@@ -461,6 +471,10 @@ void VNCSConnectionST::desktopReady()
   SConnection::desktopReady();
 }
 
+void VNCSConnectionST::setDesktopSizeDone(uint16_t result)
+{
+  writer()->writeDesktopSize(reasonClient, result);
+}
 
 void VNCSConnectionST::approveConnectionOrClose(bool accept,
                                                 const char* reason)
@@ -699,7 +713,6 @@ void VNCSConnectionST::framebufferUpdateRequest(const core::Rect& r,
 void VNCSConnectionST::setDesktopSize(int fb_width, int fb_height,
                                       const ScreenSet& layout)
 {
-  unsigned int result;
   char buffer[2048];
 
   vlog.debug("Got request for framebuffer resize to %dx%d",
@@ -709,12 +722,10 @@ void VNCSConnectionST::setDesktopSize(int fb_width, int fb_height,
 
   if (!accessCheck(AccessSetDesktopSize)) {
     vlog.debug("Rejecting unauthorized framebuffer resize request");
-    result = resultProhibited;
+    setDesktopSizeDoneOrClose(resultProhibited);
   } else {
-    result = server->setDesktopSize(this, fb_width, fb_height, layout);
+    server->setDesktopSizeRequest(this, fb_width, fb_height, layout);
   }
-
-  writer()->writeDesktopSize(reasonClient, result);
 }
 
 void VNCSConnectionST::fence(uint32_t flags, unsigned len, const uint8_t data[])
diff --git a/common/rfb/VNCSConnectionST.h b/common/rfb/VNCSConnectionST.h
index 5e91e2cdc6..9913924608 100644
--- a/common/rfb/VNCSConnectionST.h
+++ b/common/rfb/VNCSConnectionST.h
@@ -85,6 +85,7 @@ namespace rfb {
     void announceClipboardOrClose(bool available);
     void sendClipboardDataOrClose(const char* data);
     void desktopReadyOrClose();
+    void setDesktopSizeDoneOrClose(uint16_t result);
 
     // The following methods never throw exceptions
 
@@ -172,6 +173,7 @@ namespace rfb {
     void setDesktopName(const char *name);
     void setLEDState(unsigned int state);
     void desktopReady() override;
+    void setDesktopSizeDone(uint16_t result);
 
   private:
     network::Socket* sock;
diff --git a/common/rfb/VNCServer.h b/common/rfb/VNCServer.h
index 0456aa3a35..16de82d348 100644
--- a/common/rfb/VNCServer.h
+++ b/common/rfb/VNCServer.h
@@ -95,6 +95,9 @@ namespace rfb {
     // the pixelbuffer. Clients will be notified of the new layout.
     virtual void setScreenLayout(const ScreenSet& layout) = 0;
 
+    // FIXME: Change code comments above
+    virtual void setScreenLayoutDone(uint16_t result) = 0;
+
     // getPixelBuffer() returns a pointer to the PixelBuffer object.
     virtual const PixelBuffer* getPixelBuffer() const = 0;
 
diff --git a/common/rfb/VNCServerST.cxx b/common/rfb/VNCServerST.cxx
index 232477917a..42f4d590ae 100644
--- a/common/rfb/VNCServerST.cxx
+++ b/common/rfb/VNCServerST.cxx
@@ -88,12 +88,12 @@ VNCServerST::VNCServerST(const char* name_, SDesktop* desktop_)
   : desktop(desktop_), desktopStarted(false),
     desktopStarting(false), blockCounter(0), pb(nullptr),
     ledState(ledUnknown), name(name_), pointerClient(nullptr),
-    clipboardClient(nullptr), pointerClientTime(0),
-    comparer(nullptr), cursor(new Cursor(0, 0, {}, nullptr)),
-    renderedCursorInvalid(false),
+    clipboardClient(nullptr), resizeClient(nullptr),
+    pointerClientTime(0), comparer(nullptr),
+    cursor(new Cursor(0, 0, {}, nullptr)), renderedCursorInvalid(false),
     keyRemapper(&KeyRemapper::defInstance),
     idleTimer(this), disconnectTimer(this), connectTimer(this),
-    msc(0), queuedMsc(0), frameTimer(this)
+    resizeTimer(this), msc(0), queuedMsc(0), frameTimer(this)
 {
   slog.debug("Creating single-threaded server %s", name.c_str());
 
@@ -607,50 +607,79 @@ void VNCServerST::handleClipboardData(VNCSConnectionST* client,
   desktop->handleClipboardData(data);
 }
 
-unsigned int VNCServerST::setDesktopSize(VNCSConnectionST* requester,
-                                         int fb_width, int fb_height,
-                                         const ScreenSet& layout)
+void VNCServerST::setDesktopSizeRequest(VNCSConnectionST* requester,
+                                        int fb_width, int fb_height,
+                                        const ScreenSet& layout)
 {
-  unsigned int result;
-  std::list<VNCSConnectionST*>::iterator ci;
+
+  if (resizeClient) {
+    slog.debug("Rejecting concurrent framebuffer resize request");
+    requester->setDesktopSizeDoneOrClose(resultNoResources);
+    return;
+  }
 
   if (!rfb::Server::acceptSetDesktopSize) {
     slog.debug("Rejecting unauthorized framebuffer resize request");
-    return resultProhibited;
+    requester->setDesktopSizeDoneOrClose(resultNoResources);
+    return;
   }
 
   // We can't handle a framebuffer larger than this, so don't let a
   // client set one (see PixelBuffer.cxx)
   if ((fb_width > 16384) || (fb_height > 16384)) {
     slog.error("Rejecting too large framebuffer resize request");
-    return resultProhibited;
+    requester->setDesktopSizeDoneOrClose(resultNoResources);
+    return;
   }
 
   // Don't bother the desktop with an invalid configuration
   if (!layout.validate(fb_width, fb_height)) {
     slog.error("Invalid screen layout requested by client");
-    return resultInvalid;
+    requester->setDesktopSizeDoneOrClose(resultNoResources);
+    return;
   }
 
   // FIXME: the desktop will call back to VNCServerST and an extra set
   // of ExtendedDesktopSize messages will be sent. This is okay
   // protocol-wise, but unnecessary.
-  result = desktop->setScreenLayout(fb_width, fb_height, layout);
-  if (result != resultSuccess)
-    return result;
+  resizeClient = requester;
+  resizeTimer.start(2000);
+  desktop->setScreenLayout(fb_width, fb_height, layout);
+}
+
+void VNCServerST::setScreenLayoutDone(uint16_t result)
+{
+  std::list<VNCSConnectionST*>::iterator ci;
+
+  // This means we've timed out
+  // FIXME: This doesn't feel robust...
+  if (!resizeClient)
+    return;
+
+  if (result != resultSuccess) {
+    resizeClient->setDesktopSizeDoneOrClose(result);
+    resizeClient = nullptr;
+    resizeTimer.stop();
+    return;
+  }
 
   // Sanity check
-  if (screenLayout != layout)
+  if (screenLayout != getScreenLayout()) {
+    resizeClient = nullptr;
+    resizeTimer.stop();
     throw std::runtime_error("Desktop configured a different screen layout than requested");
+  }
 
   // Notify other clients
   for (ci = clients.begin(); ci != clients.end(); ++ci) {
-    if ((*ci) == requester)
+    if ((*ci) == resizeClient)
       continue;
     (*ci)->screenLayoutChangeOrClose(reasonOtherClient);
   }
 
-  return resultSuccess;
+  resizeClient->setDesktopSizeDoneOrClose(result);
+  resizeClient = nullptr;
+  resizeTimer.stop();
 }
 
 // Other public methods
@@ -732,6 +761,11 @@ void VNCServerST::handleTimeout(core::Timer* t)
   } else if (t == &connectTimer) {
     slog.info("MaxConnectionTime reached, exiting");
     desktop->terminate();
+  } else if (t == &resizeTimer) {
+    assert(resizeClient);
+    // FIXME: This is not robust.
+    resizeClient->setDesktopSizeDoneOrClose(resultNoResources);
+    resizeClient = nullptr;
   }
 }
 
diff --git a/common/rfb/VNCServerST.h b/common/rfb/VNCServerST.h
index 07392794fe..f1f28bbf19 100644
--- a/common/rfb/VNCServerST.h
+++ b/common/rfb/VNCServerST.h
@@ -85,6 +85,7 @@ namespace rfb {
     void setPixelBuffer(PixelBuffer* pb, const ScreenSet& layout) override;
     void setPixelBuffer(PixelBuffer* pb) override;
     void setScreenLayout(const ScreenSet& layout) override;
+    void setScreenLayoutDone(uint16_t result) override;
     const PixelBuffer* getPixelBuffer() const override { return pb; }
 
     void requestClipboard() override;
@@ -127,9 +128,9 @@ namespace rfb {
     void handleClipboardAnnounce(VNCSConnectionST* client, bool available);
     void handleClipboardData(VNCSConnectionST* client, const char* data);
 
-    unsigned int setDesktopSize(VNCSConnectionST* requester,
-                                int fb_width, int fb_height,
-                                const ScreenSet& layout);
+    void setDesktopSizeRequest(VNCSConnectionST* requester,
+                               int fb_width, int fb_height,
+                               const ScreenSet& layout);
 
     // closeClients() closes all RFB sessions, except the specified one (if
     // any), and logs the specified reason for closure.
@@ -194,6 +195,7 @@ namespace rfb {
     std::list<VNCSConnectionST*> clients;
     VNCSConnectionST* pointerClient;
     VNCSConnectionST* clipboardClient;
+    VNCSConnectionST* resizeClient;
     std::list<VNCSConnectionST*> clipboardRequestors;
 
     time_t pointerClientTime;
@@ -210,6 +212,7 @@ namespace rfb {
     core::Timer idleTimer;
     core::Timer disconnectTimer;
     core::Timer connectTimer;
+    core::Timer resizeTimer;
 
     uint64_t msc, queuedMsc;
     core::Timer frameTimer;
diff --git a/unix/w0vncserver/portals/PortalDesktop.cxx b/unix/w0vncserver/portals/PortalDesktop.cxx
index c52cf1c936..a421f17833 100644
--- a/unix/w0vncserver/portals/PortalDesktop.cxx
+++ b/unix/w0vncserver/portals/PortalDesktop.cxx
@@ -158,11 +158,11 @@ void PortalDesktop::terminate()
   kill(getpid(), SIGTERM);
 }
 
-unsigned int PortalDesktop::setScreenLayout(int /* fb_width */,
-                                            int /* fb_height */,
-                                            const rfb::ScreenSet& /*  layout */)
+void PortalDesktop::setScreenLayout(int /* fb_width */,
+                                    int /* fb_height */,
+                                    const rfb::ScreenSet& /*  layout */)
 {
-  return rfb::resultProhibited;
+  server->setScreenLayoutDone(rfb::resultProhibited);
 }
 
 void PortalDesktop::keyEvent(uint32_t keysym, uint32_t keycode, bool down)
diff --git a/unix/w0vncserver/portals/PortalDesktop.h b/unix/w0vncserver/portals/PortalDesktop.h
index bc524600f7..ecf9b45885 100644
--- a/unix/w0vncserver/portals/PortalDesktop.h
+++ b/unix/w0vncserver/portals/PortalDesktop.h
@@ -45,8 +45,8 @@ class PortalDesktop : public rfb::SDesktop
   void queryConnection(network::Socket* sock,
                        const char* userName) override;
   void terminate() override;
-  unsigned int setScreenLayout(int fb_width, int fb_height,
-                               const rfb::ScreenSet& layout) override;
+  void setScreenLayout(int fb_width, int fb_height,
+                       const rfb::ScreenSet& layout) override;
   void keyEvent(uint32_t keysym, uint32_t keycode, bool down) override;
   void pointerEvent(const core::Point& pos,
                     uint16_t buttonMask) override;
diff --git a/unix/w0vncserver/wayland/WaylandDesktop.cxx b/unix/w0vncserver/wayland/WaylandDesktop.cxx
index e4dae37ff0..b06e7b477e 100644
--- a/unix/w0vncserver/wayland/WaylandDesktop.cxx
+++ b/unix/w0vncserver/wayland/WaylandDesktop.cxx
@@ -188,6 +188,12 @@ void WaylandDesktop::terminate()
   kill(getpid(), SIGTERM);
 }
 
+void WaylandDesktop::setScreenLayout(int /*fb_width*/, int /*fb_height*/,
+                                     const rfb::ScreenSet& /*layout*/)
+{
+  server->setScreenLayoutDone(rfb::resultProhibited);
+}
+
 void WaylandDesktop::handleClipboardRequest()
 {
   if (!dataControl)
diff --git a/unix/w0vncserver/wayland/WaylandDesktop.h b/unix/w0vncserver/wayland/WaylandDesktop.h
index b12b4658ff..72dee855df 100644
--- a/unix/w0vncserver/wayland/WaylandDesktop.h
+++ b/unix/w0vncserver/wayland/WaylandDesktop.h
@@ -24,7 +24,7 @@
 
 #include <rfb/SDesktop.h>
 
-namespace rfb { class VNCServer; }
+namespace rfb { class VNCServer; struct ScreenSet; }
 
 namespace wayland {
   class Output;
@@ -55,6 +55,9 @@ class WaylandDesktop : public rfb::SDesktop {
                         const char* userName) override;
   void terminate() override;
 
+  void setScreenLayout(int fb_width, int fb_height,
+                       const rfb::ScreenSet& layout) override;
+
   virtual void handleClipboardRequest() override;
   virtual void handleClipboardAnnounce(bool available) override;
   virtual void handleClipboardData(const char* data) override;
diff --git a/unix/x0vncserver/XDesktop.cxx b/unix/x0vncserver/XDesktop.cxx
index b52b20e199..6f9037981d 100644
--- a/unix/x0vncserver/XDesktop.cxx
+++ b/unix/x0vncserver/XDesktop.cxx
@@ -687,14 +687,15 @@ static void GetSmallerMode(XRRScreenResources *res,
 }
 #endif /* HAVE_XRANDR */
 
-unsigned int XDesktop::setScreenLayout(int fb_width, int fb_height,
-                                       const rfb::ScreenSet& layout)
+void XDesktop::setScreenLayout(int fb_width, int fb_height,
+                               const rfb::ScreenSet& layout)
 {
 #ifdef HAVE_XRANDR
   XRRScreenResources *res = XRRGetScreenResources(dpy, DefaultRootWindow(dpy));
   if (!res) {
     vlog.error("XRRGetScreenResources failed");
-    return rfb::resultProhibited;
+    server->setScreenLayoutDone(rfb::resultProhibited);
+    return;
   }
   vncSetGlueContext(dpy, res);
 
@@ -741,26 +742,30 @@ unsigned int XDesktop::setScreenLayout(int fb_width, int fb_height,
     if (outputId == None) {
       vlog.debug("Resize adjust: Could not find corresponding screen");
       XRRFreeScreenResources(res);
-      return rfb::resultInvalid;
+      server->setScreenLayoutDone(rfb::resultInvalid);
+      return;
     }
     XRROutputInfo *output = XRRGetOutputInfo(dpy, res, outputId);
     if (!output) {
       vlog.debug("Resize adjust: XRRGetOutputInfo failed");
       XRRFreeScreenResources(res);
-      return rfb::resultInvalid;
+      server->setScreenLayoutDone(rfb::resultInvalid);
+      return;
     }
     if (!output->crtc) {
       vlog.debug("Resize adjust: Selected output has no CRTC");
       XRRFreeScreenResources(res);
       XRRFreeOutputInfo(output);
-      return rfb::resultInvalid;
+      server->setScreenLayoutDone(rfb::resultInvalid);
+      return;
     }
     XRRCrtcInfo *crtc = XRRGetCrtcInfo(dpy, res, output->crtc);
     if (!crtc) {
       vlog.debug("Resize adjust: XRRGetCrtcInfo failed");
       XRRFreeScreenResources(res);
       XRRFreeOutputInfo(output);
-      return rfb::resultInvalid;
+      server->setScreenLayoutDone(rfb::resultInvalid);
+      return;
     }
 
     unsigned int swidth = iter->dimensions.width();
@@ -797,7 +802,8 @@ unsigned int XDesktop::setScreenLayout(int fb_width, int fb_height,
     } else {
       vlog.error("Failed to find smaller or equal screen size");
       XRRFreeScreenResources(res);
-      return rfb::resultInvalid;
+      server->setScreenLayoutDone(rfb::resultInvalid);
+      return;
     }
   }
 
@@ -827,20 +833,22 @@ unsigned int XDesktop::setScreenLayout(int fb_width, int fb_height,
      VNCSConnectionST::setDesktopSize. Another ExtendedDesktopSize
      with reason=0 will be sent in response to the changes seen by the
      event handler. */
-  if (adjustedLayout != layout)
-    return rfb::resultInvalid;
+  if (adjustedLayout != layout) {
+    server->setScreenLayoutDone(rfb::resultInvalid);
+    return;
+  }
 
   // Explicitly update the server state with the result as there
   // can be corner cases where we don't get feedback from the X server
   server->setScreenLayout(computeScreenLayout());
 
-  return ret;
+  server->setScreenLayoutDone(ret);
 
 #else
   (void)fb_width;
   (void)fb_height;
   (void)layout;
-  return rfb::resultProhibited;
+  server->setScreenLayoutDone(rfb::resultProhibited);
 #endif /* HAVE_XRANDR */
 }
 
diff --git a/unix/x0vncserver/XDesktop.h b/unix/x0vncserver/XDesktop.h
index 89e2531dbb..7e73e87003 100644
--- a/unix/x0vncserver/XDesktop.h
+++ b/unix/x0vncserver/XDesktop.h
@@ -66,8 +66,8 @@ class XDesktop : public rfb::SDesktop,
   void pointerEvent(const core::Point& pos,
                     uint16_t buttonMask) override;
   void keyEvent(uint32_t keysym, uint32_t xtcode, bool down) override;
-  unsigned int setScreenLayout(int fb_width, int fb_height,
-                               const rfb::ScreenSet& layout) override;
+  void setScreenLayout(int fb_width, int fb_height,
+                       const rfb::ScreenSet& layout) override;
   void handleClipboardRequest() override;
   void handleClipboardAnnounce(bool available) override;
   void handleClipboardData(const char* data) override;
diff --git a/unix/xserver/hw/vnc/XserverDesktop.cc b/unix/xserver/hw/vnc/XserverDesktop.cc
index 5e8164274f..828cf642ac 100644
--- a/unix/xserver/hw/vnc/XserverDesktop.cc
+++ b/unix/xserver/hw/vnc/XserverDesktop.cc
@@ -482,8 +482,8 @@ void XserverDesktop::pointerEvent(const core::Point& pos,
   vncPointerButtonAction(buttonMask);
 }
 
-unsigned int XserverDesktop::setScreenLayout(int fb_width, int fb_height,
-                                             const rfb::ScreenSet& layout)
+void XserverDesktop::setScreenLayout(int fb_width, int fb_height,
+                                     const rfb::ScreenSet& layout)
 {
   unsigned int result;
 
@@ -494,7 +494,7 @@ unsigned int XserverDesktop::setScreenLayout(int fb_width, int fb_height,
   // can be corner cases where we don't get feedback from the X core
   refreshScreenLayout();
 
-  return result;
+  server->setScreenLayoutDone(result);
 }
 
 void XserverDesktop::frameTick(uint64_t msc)
diff --git a/unix/xserver/hw/vnc/XserverDesktop.h b/unix/xserver/hw/vnc/XserverDesktop.h
index 036cf9d201..b8b732c921 100644
--- a/unix/xserver/hw/vnc/XserverDesktop.h
+++ b/unix/xserver/hw/vnc/XserverDesktop.h
@@ -100,8 +100,8 @@ class XserverDesktop : public rfb::SDesktop, public rfb::FullFramePixelBuffer,
   void pointerEvent(const core::Point& pos,
                     uint16_t buttonMask) override;
   void keyEvent(uint32_t keysym, uint32_t keycode, bool down) override;
-  unsigned int setScreenLayout(int fb_width, int fb_height,
-                               const rfb::ScreenSet& layout) override;
+  void setScreenLayout(int fb_width, int fb_height,
+                       const rfb::ScreenSet& layout) override;
   void frameTick(uint64_t msc) override;
   void handleClipboardRequest() override;
   void handleClipboardAnnounce(bool available) override;
diff --git a/win/rfb_win32/SDisplay.cxx b/win/rfb_win32/SDisplay.cxx
index de986ead1c..ac5bc8e5c5 100644
--- a/win/rfb_win32/SDisplay.cxx
+++ b/win/rfb_win32/SDisplay.cxx
@@ -170,6 +170,10 @@ void SDisplay::queryConnection(network::Socket* sock,
   server->approveConnection(sock, true);
 }
 
+void SDisplay::setScreenLayout(int /*fb_width*/, int /*fb_height*/,
+                              const rfb::ScreenSet& /*layout*/) {
+  server->setScreenLayoutDone(rfb::resultProhibited);
+}
 
 void SDisplay::startCore() {
 
diff --git a/win/rfb_win32/SDisplay.h b/win/rfb_win32/SDisplay.h
index e116b483a9..2c5deb25a7 100644
--- a/win/rfb_win32/SDisplay.h
+++ b/win/rfb_win32/SDisplay.h
@@ -79,6 +79,8 @@ namespace rfb {
       void terminate() override;
       void queryConnection(network::Socket* sock,
                            const char* userName) override;
+      void setScreenLayout(int fb_width, int fb_height,
+                           const ScreenSet& layout) override;
       void handleClipboardRequest() override;
       void handleClipboardAnnounce(bool available) override;
       void handleClipboardData(const char* data) override;