diff --git a/vncviewer/parameters.h b/vncviewer/parameters.h
index a935ea0..59909d1 100644
--- a/vncviewer/parameters.h
+++ b/vncviewer/parameters.h
@@ -39,6 +39,9 @@
 
 #ifdef HAVE_FLTK_FULLSCREEN
 extern rfb::BoolParameter fullScreen;
+#ifdef HAVE_FLTK_FULLSCREEN_SCREENS
+extern rfb::BoolParameter fullScreenAllMonitors;
+#endif // HAVE_FLTK_FULLSCREEN_SCREENS
 #endif // HAVE_FLTK_FULLSCREEN
 extern rfb::StringParameter desktopSize;
 extern rfb::BoolParameter remoteResize;