diff -up tigervnc-1.3.0/vncviewer/Viewport.cxx.cursor tigervnc-1.3.0/vncviewer/Viewport.cxx
--- tigervnc-1.3.0/vncviewer/Viewport.cxx.cursor	2013-12-17 13:28:23.170400013 +0000
+++ tigervnc-1.3.0/vncviewer/Viewport.cxx	2013-12-17 13:29:46.095784064 +0000
@@ -248,7 +248,7 @@ void Viewport::setCursor(int width, int height, const Point& hotspot,
     }
   }

-  if (Fl::belowmouse() == this)
+  if (Fl::belowmouse() == this && cursor)
     window()->cursor(cursor, cursorHotspot.x, cursorHotspot.y);
 }