diff --git a/vncviewer/cocoa.h b/vncviewer/cocoa.h
index 3bbe6fa..8798082 100644
--- a/vncviewer/cocoa.h
+++ b/vncviewer/cocoa.h
@@ -19,7 +19,7 @@
 #ifndef __VNCVIEWER_COCOA_H__
 #define __VNCVIEWER_COCOA_H__
 
-int cocoa_capture_display(Fl_Window *win);
+int cocoa_capture_display(Fl_Window *win, bool all_displays);
 void cocoa_release_display(Fl_Window *win);
 
 #endif