diff --git a/vncviewer/parameters.h b/vncviewer/parameters.h
index 9ce56b9..2ccd928 100644
--- a/vncviewer/parameters.h
+++ b/vncviewer/parameters.h
@@ -55,6 +55,7 @@
 extern rfb::BoolParameter sendClipboard;
 #if !defined(WIN32) && !defined(__APPLE__)
 extern rfb::BoolParameter sendPrimary;
+extern rfb::StringParameter display;
 #endif
 
 extern rfb::StringParameter menuKey;