diff --git a/CMakeLists.txt b/CMakeLists.txt
index d9709c809..8fdd7d024 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -704,6 +704,12 @@ if(WITH_LIBVNCSERVER)
   )
 endif(WITH_LIBVNCSERVER)
 
+if(WITH_LIBVNCCLIENT)
+  list(APPEND SIMPLETESTS
+    client_capstest
+  )
+endif(WITH_LIBVNCCLIENT)
+
 
 if(WITH_THREADS AND (CMAKE_USE_PTHREADS_INIT OR CMAKE_USE_WIN32_THREADS_INIT) AND WITH_LIBVNCSERVER AND WITH_LIBVNCCLIENT)
   set(SIMPLETESTS
@@ -759,6 +765,9 @@ endif(LIBVNCSERVER_WITH_WEBSOCKETS AND WITH_LIBVNCSERVER)
 if(WITH_LIBVNCSERVER)
   add_test(NAME cargs COMMAND test_cargstest)
 endif(WITH_LIBVNCSERVER)
+if(WITH_LIBVNCCLIENT)
+  add_test(NAME client_caps COMMAND test_client_capstest)
+endif(WITH_LIBVNCCLIENT)
 if(UNIX)
   if(WITH_LIBVNCSERVER)
     add_test(NAME includetest_server COMMAND ${TESTS_DIR}/includetest.sh ${CMAKE_INSTALL_PREFIX}/${CMAKE_INSTALL_INCLUDEDIR} ${CMAKE_MAKE_PROGRAM} "rfb/rfb.h")
diff --git a/src/libvncclient/rfbclient.c b/src/libvncclient/rfbclient.c
index f6baf641c..4c1eef351 100644
--- a/src/libvncclient/rfbclient.c
+++ b/src/libvncclient/rfbclient.c
@@ -1709,6 +1709,11 @@ SendExtDesktopSize(rfbClient* client, uint16_t width, uint16_t height)
     return TRUE;
   }
 
+  if (!SupportsClient2Server(client, rfbSetDesktopSize)) {
+    rfbClientLog("Server does not support SetDesktopSize - not sending dimensions %dx%d\n", width, height);
+    return TRUE;
+  }
+
   if (client->screen.width != rfbClientSwap16IfLE(width) || client->screen.height != rfbClientSwap16IfLE(height)) {
     rfbClientLog("Sending dimensions %dx%d\n", width, height);
     sdm.type = rfbSetDesktopSize;
@@ -2154,6 +2159,9 @@ HandleRFBServerMessage(rfbClient* client)
       }
 
       if (rect.encoding == rfbEncodingExtDesktopSize) {
+        /* A server that sends ExtendedDesktopSize must understand SetDesktopSize. */
+        SetClient2Server(client, rfbSetDesktopSize);
+
         /* read encoding data */
         int screens;
         int loop;
diff --git a/test/client_capstest.c b/test/client_capstest.c
new file mode 100644
index 000000000..eb1ded082
--- /dev/null
+++ b/test/client_capstest.c
@@ -0,0 +1,26 @@
+#include <rfb/rfbclient.h>
+
+int main(void)
+{
+  rfbClient* client;
+
+  client = rfbGetClient(8, 3, 4);
+  if (!client)
+    return 1;
+
+  client->screen.width = rfbClientSwap16IfLE(640);
+  client->screen.height = rfbClientSwap16IfLE(480);
+
+  if (SupportsClient2Server(client, rfbSetDesktopSize)) {
+    rfbClientCleanup(client);
+    return 1;
+  }
+
+  if (!SendExtDesktopSize(client, 800, 600)) {
+    rfbClientCleanup(client);
+    return 1;
+  }
+
+  rfbClientCleanup(client);
+  return 0;
+}