diff --git a/ChangeLog.md b/ChangeLog.md
index 62ea71992..c493d8c56 100644
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -79,6 +79,11 @@ the SSH connection timeout specified using the `ConnectTimeout` OpenSSH config
 file keyword was interpreted as milliseconds rather than seconds.  This caused
 the SSH connection to fail if the timeout was too low.
 
+16. Fixed an issue whereby the Java TurboVNC Viewer threw an
+IllegalComponentStateException if "Remote desktop size" was changed to "Auto"
+in the TurboVNC Viewer Options dialog while the viewer was actively receiving
+framebuffer updates from a VNC server.
+
 
 2.2.9 ESR
 =========
diff --git a/java/com/turbovnc/vncviewer/CConn.java b/java/com/turbovnc/vncviewer/CConn.java
index 6f6c1d6ae..1ad513d5c 100644
--- a/java/com/turbovnc/vncviewer/CConn.java
+++ b/java/com/turbovnc/vncviewer/CConn.java
@@ -1,6 +1,6 @@
 /* Copyright (C) 2002-2005 RealVNC Ltd.  All Rights Reserved.
  * Copyright 2009-2011 Pierre Ossman <ossman@cendio.se> for Cendio AB
- * Copyright (C) 2011-2023 D. R. Commander.  All Rights Reserved.
+ * Copyright (C) 2011-2023, 2025 D. R. Commander.  All Rights Reserved.
  * Copyright (C) 2011-2015 Brian P. Hinz
  *
  * This is free software; you can redistribute it and/or modify
@@ -1763,9 +1763,11 @@ public void getOptions() {
 
     if (options.fullScreen.isSelected() != opts.fullScreen)
       toggleFullScreen();
-    else if (recreate)
-      recreateViewport();
-    else if (reconfigure)
+    else if (recreate) {
+      synchronized (this) {
+        recreateViewport();
+      }
+    } else if (reconfigure)
       reconfigureAndRepaintViewport(false);
     if (deleteRestore) {
       savedState = -1;
@@ -1793,7 +1795,9 @@ public void toggleToolbar() {
       return;
     showToolbar = !showToolbar;
     if (viewport != null) {
-      recreateViewport();
+      synchronized (this) {
+        recreateViewport();
+      }
       viewport.showToolbar(showToolbar);
     }
     menu.showToolbar.setSelected(showToolbar);
@@ -1803,8 +1807,11 @@ public void toggleToolbar() {
   public void toggleFullScreen() {
     opts.fullScreen = !opts.fullScreen;
     menu.fullScreen.setSelected(opts.fullScreen);
-    if (viewport != null)
-      recreateViewport(true);
+    if (viewport != null) {
+      synchronized (this) {
+        recreateViewport(true);
+      }
+    }
   }
 
   public boolean shouldGrab() {