diff --git a/vncviewer/Viewport.cxx b/vncviewer/Viewport.cxx
index a12f783..1e4ee1a 100644
--- a/vncviewer/Viewport.cxx
+++ b/vncviewer/Viewport.cxx
@@ -403,6 +403,9 @@
 
   assert(self);
 
+  if (!sendClipboard)
+    return;
+
 #if !defined(WIN32) && !defined(__APPLE__)
   if (!sendPrimary && (source == 0))
     return;